I just wanted to follow up on the results of our little discussion a month ago. I did end up getting a Polk LSiM 706c for my center, and I think this was the right choice. I overlooked how important it is to have the centers match your towers. The 706's blend extraordinarily well with the 707s, and I think I would be very very hard press trying to find a better center for those 707s. I also picked up a Parasound HCA-1500a (and in great condition for $250!) two channel amplifier to drive the 707s, and let me tell you, the difference in sound was immediate. I was blown away on how much better the 707s sounded with proper amplifier. For a week or so while I was looking for an amplifier I was feeding my Yamaha AV-1600 (120W) amplifier from the preout of the Marantz NR-1402 (the AV-1600 is having HDMI handshaking problems which is why I wasn't using it on it's own) and there was an improvement over the Marantz NR-1402 on it's own. But the moment I replaced the yamaha AVR with the parasound amp there was no comparison--the sound was in a completely different ball game. I guess I was always just under the impression that more watts means louder sound. Now I'm starting to think, in simplest terms possible, that watts determine limits for the area under the SPL to frequency graph, and when your amp just doesn't have the capability feed power hungry speakers than, while you may still hear loud sound, other frequencies may be curtailed--and most prominently in the lower frequencies. Certainly no one wants to blow their doors down with a 1Khz (and only 1Khz) tone, for instance
. Of course this is oversimplified, but I think this is a picture I like to keep mind.
I still plan on replacing the Marantz with a receiver that offers preamp support and either grabbing me a 3 channel amp from Emotiva or possibly just adding a mono-amp and keep the parasound for the 707s. I'm not yet sure if I'm comfortable having two different manufacturers of amps powering my fronts and center. But for now, the wife has cut the home theater spending for a bit--at least have a great setup for listening to music and I am much happier with my movie experience compared to one month ago.