Jack, my first thought was what Beetle suggested, but turning the room around is a very big deal, and listening from the dining room is probably a goal . . . 5' is a lot, and somewhat more than necessary, but more is better to separate the direct from reflected wavefront. But 2' is not enough. The auditory brain tries to integrate sources separated by less than a few milliseconds. We are testing.
Your equipment is great and as you say, should not be the problem. However, bridged amps are less comfortable driving low impedance loads. The 7b has huge power, so matching impedance is probably more critical than power. I don't know the circuit of that amp to make a recommendation. Experiment and let us know.
I do know that my first approach to upgrading the CS5 would be to separate the bass drivers (3x 8" on 2 bass circuits) from the uppers with 4 identical amp channels running the pair of speakers. At the 400 Hz lower midrange crossing, the impedance is 4 ohms and rising slowly, which presents a sweet resistive load for the upper amp. The bass current draw would be sequestered in its own channel.
Your problem is the core problem that limited the life and acceptance of the CS5. Both at the time and more so in hindsight, I believe a 4 channel setup for the CS5 might have made it a success.
