Onkyo HT-S5100 or Onkyo TX-SR606 + Speakears

As far as the 2 Onkyos you've mentioned I would recommend the 606 receiver. With the ability to decode all the new lossless audio codecs you'll have a lot more flexibility with this receiver for future applications, such as adding a blu-ray player that can't decode lossless audio internally.

Personally I use Onkyo speakers and I think they sound great. However, the vast majority of people on here say they sound like crap compared to Polk. I don't know about HK. They seem to have a good reputation though. I've never done any comparisons myself. How you wire them can make a difference though. For some unorthodox wiring tips see the following link:
http://avtruths.com/budgetcables.html
Good luck with your setup.
By the way, the link you posted for the HK doesn't work.

I have the Onkyo HT-S894 system with the HT-R650 receiver.
I've been looking at upgrading the speakers.

Infinity Beta 20s $220 for a pair
Infinity Beta 10s $178 for a pair
Infinity Beta C250 $119.
Still undecided on a Sub
The HSU VTF-1 Sub has good reviews but is $432

Check out the website vanns.com

I have not personally ever heard those speakers in action. The set I have can be found here:
http://www.onkyousa.com/model.cfm?m=...ss=Speaker&p=i

The only complaint I had against them was that I had a hard time finding speaker stands to work with them because their shape is a little unusual. Other than that I've been very satisfied with them.

And Tacoboy is right about vanns.com. You can get some great deals there plus free shipping. For any wires you need, buy from monoprice.com for the best prices. Six foot v1.3a HDMI cables can be bought for as little as $4.05 plus shipping. I am currently using 2 of these and they work great. No reason to pay what they're charging in stores.

I was in basically the same predicament as you. I was torn between the Onkyo 605 and the SR-800 HTib (the models you are looking at are just this years versions essentially).

Ultimately, I worked it out in my head like this.

I'd like the lossless codecs, but currently I don't have a Blu-ray player and my HD-DVD player (Xbox 360 add-on) doesn't have the capability anyway. Also, when I do decide to get a Blu-ray player, if I get one with 7.1 analog outs and onboard decoding (Sony is releasing one this fall), then I'll still be able to get them with the receiver in the SR-800.

Ultimately, the SR-800 was cheaper, included speakers, and had nearly all of the capabilities of the 605. I've been extremely happy with the SR-800 (this years version - 5100 seems equivalent).

Good Luck!