Looking to upgrade

My current system is:

Yamaha rx-v471 receiver
Mirage Omni C150 for center
2 Mirage Omni 550 for front
2 Mirage Omni 150 for surround
Infinity BU-2 subwoofer

I use this only for watching movies/tv. I recently got a projector, so the huge screen just makes my sound seem that much more weak. My room is 12'x12'.

My primary problem is that dialogue is low volume. This is confirmed by YPAO, which tries to set the center channel at +6 dB. This, of course, is not a good idea and results in lots of distortion. The Mirage center only has a sensitivity of 87 dB.

I am thinking of replacing at least the front speakers with something more efficient. I would probably go with all bookshelf speakers like maybe 3 Klipsch RB-61 II or RB-81 II. I may even get 5 identical speakers. It seems like this may sound ok and I could replace the receiver to something with more power later on if necessary. Or I could just get a more powerful receiver and see if that helps the Mirage speakers. I also plan to replace the sub at some point. I've had it for almost 20 years but still works fine, although it's a bit boomy.

What does everyone think? It looks like many people battle the problem of weak dialogue. I want to make sure I fix this if I start spending money.

I could spend $1000 on the front 3 or maybe $1500 if I was replacing all 5 speakers.

I'm willing to wait awhile for a good deal. So I could watch for something even more expensive to go on sale. I could probably also go higher in price if I don't end up replacing the receiver.

I will get a new sub after I get the center channel issues resolved.

YPAO set the sub to -10 dB. It set the surrounds to -1 dB, The front speakers to 0 dB, and the center to +6 dB.

There was almost no bass at that level so I set the sub back to 0. I wouldn't consider the sub to be loud at this level. Like I said, it's kind of boomy, so I don't run it too hard.

I didn't think about this too much. Looking around the forums, it seems there are plenty of other people where YPAO messes up the sub.

Would it be a good idea to get 3 IQ70s and use one of them for the center channel? My projector screen is mounted high enough that an IQ70 would fit under it.

As for receiver upgrade, what about the Harman Kardon 3600? Refurbs on ebay go for $400 and have warranty. It seems much more powerful with the discrete channels than my Yamaha, and it has pre-outs. Or is there something I'm missing and this is a waste of money?