OK, I've spent a little time with google and want to revise my previous comments somewhat. I still recommend the Model 990, but I don't believe that you can part with the Yamaha entirely just yet without adding some more amplification. Here's why...
I found what appears to be
some information on your Carver amps that raised a question for me. If I understand correctly, your only two amps (Carver M-1.0t's) are two-channel amps that has been bridged into mono (presumably to drive one of the Polk 1.2TL's). That leaves the FXi30's and CSi30 looking for power from somewhere else. That somewhere else is the Yamaha. Your Yamaha is a
curious beast - it has a three-channel amp built in to it. Based on the manual I got from that Amazon.com link, you can continue to use the Yamaha as an amp. It has a selector switch on it labeled "processor selector." If you set it to "external" then the Yamaha can act purely as a power amp - volume control, tone control, and everything else (even input selection) will be disabled on the Yamaha. I would recommend either doing that or replacing the Yamaha with separate amps (perhaps a trio of Outlaw M2200's). Probably the best place to start would be to keep the Yamaha in place, set it to "external processing," and use it as amp for the center and surrounds while the pair of Carver amps handle the mains and a Model 990 serves as processor. In that scenario, you'd connect the center and surround pre-amp outputs from the 990 to the three appropriate "INPUT from AMP/RECEIVER PREOUT" inputs near the top center of the Yamaha's rear panel. At some later date, you can always upgrade your amplification by replacing the Yamaha.