Adding a Klipsch RC-64

Yeah its gonna be lopsided for sure. If your going with towers to replace the fronts later like the RF 62 Or RF 63 then I would get the RC 64, if you only plan on bookshelfs or smaller towers then go with the RC 62. The Klipsch Reference series speakers are very effience, so all you other speakers are going to sound kinda weak.

Try to atleast match the driver size and get the RF62's or better. I run the RC64 with RF82's and love it.

The RF 52's are 5.25" woofers and the RC 64 uses 6.5" woofers. If budget is tight you should try to invest evenly, so what I myself would do is go with the RC 62 and get the RF62 towers, that would match better than the RC 64 with the RF 52. Go with the RC 62 and RF 62s would be cheaper than going with the RC 64 and RF 52s. If you really stuck on the RC 64 and your getting a good deal then jump on it. I myself wouldn't have replaced the Onkyo 705 with the 608, but both are more than capable of powering the Klipschs.

It wouldn't completely overpower your mains because you could level match your speakers, but I would think there would be a considerable tonal difference and you would notice the weakness in your SLX mains.

I've demoed the 64 and owned the 62... the 64 goes a tad lower but other than that the RC-62 was a great authoritive center and filled my 14x18 accoustically treated movie room with ease from 15' away where I sit. I also owned the RF-82 which were also superb and after demoing them next to the much higher priced 63 I didn't think the 63's were worth the difference in price.

In the end the Klipsch sound (fatiguing harsh sound that many Klipsch dislikers and haters that can hear above 18k complain about ) got to me and my wife.

Also be aware that the Klipsch's have very sensitive tweeters but the woofers are stiff and require a kick in the but (external amp) to really open up... without it they sounded small and the tweeters outplayed the woofers... the audio botique I bought them from told me this would be the case and they were right. With the amp the difference was night and day. If you can't hear above 15k or so and feed them good power you'll probably love them.. they are nice speakers and do a lot really, really well...

just audition them extensively as the fatigue may take 30 minutes of steady listening to get to you... if it does you'll want to run out of the room.

Also to get as close to timbre matching as possible the RC62 shares tweets with the RF62 and 82... the RC64 has a different tweet which is used in the RF63 and 83.

I am curious what AVR was hooked up to both the RF-82 HT and the RF-63 HT in the store and what was driving what you eventually brought home?

Sony ES with Parasound amp. in store demo room switchable from 63 to 82 and Paradigm Monitor 11.... sounded a little scratch in parts of John Mayer Concert but figured i'd try anyways.

At home in treated theater room..Yamaha HTR5860...weak alone..then amped with Behringer EP1500 and then Emotiva XPA-3. Stronger bass and mids...but after 30 min. too fatiguing to handle.. my wife experienced this as well... of course many, many, many peopele experience the same thing.

That's why people either love or hate Klipsch...I can hear over 19k... which is very very good for a teenager much less someone in thier mid 30s. I'm not a hater.. I like the THX-650 alot.. but the RF line gets to me like a dog whistle... although they image superbly and have the ability to really project detail.

I am not going to comment about you being able to hear "over 19K," let alone having a wife that can as well. I also can't argue that some people don't like Klipsch speakers...That being said, your audition of the RF-82 HT and preferring it over the RF-63 makes me wonder what was different in the setup at the store, because the latter was actually designed to be a "warmer" speaker (as well as the RC-64) than the lower end models or the previous upper end Reference.

Insofar as what you experience in your home using a lower end Yamaha (with or without separate amplification) may be in they Yamaha processing which definitely can add to the "harshness" you and your wife were hearing. I am not calling you a "hater," but if your superior hearing "likes" what it hears in the Klipsch THX Kl-650 and didn't recognize any discomfort in the store with the RF-82/RC-62, I contend there could be an ulterior explanation.

Regardless, this is OT for this thread and doesn't address the OP's situation.

As for my hearing I work for the Gov. and have my hearing tested every few years... and I did hear slight harshness in the demo room...I just thought they did everything else so well I blew it off and wanted to give them a chance. As for the gear I used no DSP so the amps each lent their own sound to the speakers... It can't be denied that many many people experience ear bleeding discomfort with Klipsch... I was hoping I would not be on of them... ohh well...

Back to the OP.

Go with a good all around 5.1 system than trying to squeeze a 7.1 into your budget. 1 pair of good surround speakers is better than 2 pair of cheaper ones, not much happening in those other 2 channels in a 7.1 to worry about, if on a some what tight budget.

If your AVR has DPLIIx it may be worth going to a 7.1 speaker system... DPLIIx creates the rears from the surround info imbeded it 5.1 tracks, and does a good job at it... if your receiver is just a standard 7.1 and can't create or mimic the rears then I wouldn't bother... it's very rare that a Blu-ray comes out with 7.1 discrete channels..rare meaning almost never.. which is a shame.. I don't know why 7.1 isn't the standard.

I see a lot of people come on here and be sort of apologetic about the equipment that they own, I hate to see that since everyone is doing the best they can with the budget they have and what they know at the time.

When I made the move to DVD (from VHS) I bought a JVC 5.1 channel AVR to replace the old Sansui stereo receiver and I built my surround speaker system out of the various stereo speakers I picked up through out the years.
I enjoyed that system imensely for 10 years and only recently replaced it with an up to date AVR and 'matched' speakers.
The new audio system definitely sounds better than the vintage collection I had been using, but the old system was good enough that I had to spend a bunch of money to get better.

The very first "upgrade" I made was to replace the center channel with a RC-62.
This speaker single handedly made the biggest change to my system, the RC-62 is/was a huge upgrade over the old center channel; so much so that it 'inspired' me to start looking at new mains and eventually new surrounds.

The RC-64 is a beast and it is the flagship center channel in the Reference Series. Nothing negative to say about it at all performance wise and the output level can be matched to the other speakers so if this is what you want I will not discourage you from getting it.
However there are compromises to be made with everything and the drawbacks to the RC-64 is its size and price. The RC-64 is huge so it may present placement challenges and it costs double what the RC-62 costs.

Each individual has to decide for themselves if the price verse performance is worth it, I chose the RC-62 because it fit where it needed to fit.
I have not been disappointed with the performance in any way, it is an excellent center channel speaker in its own right.

In my opinion the RC-62 would be as big of an upgrade to your system as it was in mine so you would get a great wow factor out of it, plus it costs a lot less than the RC-64; which as you pointed out gives you some money to spend/save for new fronts.

If I had your existing system I would do the center channel upgrade first then save for the best Reference Series tower you can justify.

When it comes to timbre matching some people are real sticklers about it, I guess I am not a hard core timbre matching kind of guy.
In my completely non-scientific never heard your speakers before opinion, the RC-64 and the RC-62 will both match your SLX fronts (or any of the Reference towers or bookshelf speakers that may be in your future) better than the Optimus center matches the SLX fronts now.

BTW, the SLX speakers will make excellent surround speakers if you do decide to get new front speakers.

The 62 is no slouch... it has superb imaging and extrememly clear vocals... I personally don't think the 64 is worth the money compared to the 62 (I actually came very very close to getting the 64 until demoing them A/B) .... not only that If you get a 64 to properly timber match to the 64 you'll be forced to get the more expensive RF63 and 83... (Klipsch claims the entire RF line is timber matched..but most like to keep the same tweeters matched if not the entire speaker) which once again the cheaper RF82 is a great speaker itself...It's imaging rivaled the Paradigm studio 100s and matched the 63s when I domoed them... and the gain in performance to the 63/83 is minimal but it may be worth it to some who aren't on a bang for your buck budget and just want the flagship... or think the small difference is worth the much higher price.

With some good power the 62 can easily fill a large home theater to reference levels sitting 15' back and probably even a little further.

Just something to think about!

I'm not a Klipsch guy but...if you are, it's a great speaker.