Stereo Guy wants center channel

Ok, first time poster here. I'm looking for 2 suggestions and I'll get to those shortly.

Here is what I'm currently running. I listen to a lot of music and this is in a 1600 sq ft loft. This is why I'm running two subs.

sources are DVR, apple tv, playstation for blue ray and compact discs

ONKYO TX-8511 - 100 watts per channel solid state - Purchased 15 years ago in college

Infinity Kappa 5.1 Series II mains - will take 150 watts per channel and are 90db sensitivity - Purchased 15 years ago in college. I've replaced the 8" woofers once.

dual Martin Logan Abyss subs - Purchased 6 years ago.

I'm running each sub with speaker level inputs off the bi-amps on the Kappas. So I'm running full range into the kappas, which naturally fall off at 50hz and the subs pick up the bottom end. I'm quite happy with this arrangement and don't want to change this aspect of the system.

Please excuse me if my terms aren't correct as I haven't researched this stuff in quite a while. I've never been interested in home theater before, however I'm finding something annoying watching movies with this system. The dialogue is at a much lower level than action sequences and I find myself constantly turning the volume up for dialogue and down for action. So I'm looking to add a center channel to my system and a receiver that does home theater stuff. I'm not really interested in adding rear speakers because I largely listen to music and I just don't care that much right now. I just want movie watching to be a little more enjoyable. So my plan is to run 3.1 and my understanding is that 5.1 receivers can downmix to 3.1 to satisfy my need.

I don't know anything about current receiver technology accept that the HDMI switching stuff interests me. I like the idea of running all the HDMI into the receiver and only having one HDMI into the television. I also know that it used to be that integrated circuit amps were crap and solid state amps, like the little Onkyo I have were somewhat better. Perhaps the newer digital amps, like in car audio, exist in home products? I don't know.

I'd like a substantial center channel and it seems like a no brainer to pick up a used Infinity Kappa Video and run that as my center. It should match well with my mains and is 89db sensitivity, so very close. I'm not opposed to having speakers in the unit repaired if this is a good center channel choice.

I'd like a stout amplifier. My mains will take 150 watts and that center will take 150 watts, so I'm not opposed to spending money on something with decent power. When I get out of this loft and into a house, I'd probably be interested in running rears and would probably just pick up another pair of Kappa 5.1's.

So based on all this I'm looking for the following recommendations.

Reciever (I'll also consider multiple components here, but would rather keep it simple)

Center channel

Just to clarify, the receiver should push full range to the mains and run the center for now. And it will push rears sometime in the future.

My ears are open :-)