Glen, to keep it short, i'm driving my CS7.2s with a Classe Omega Omicron amp, 350/700/1400 wpc. I have an Aerial CC3b for my center, and Paradigm Ref ADPs for surrounds. These are driven by a Parasound HCA-2205 5x220 wpc amp. The rest of my system consists of a M&K 350THX sub, Meridian 561, Sony DVP7700, and Sony W400Q projector. For two channel I have a Meridian 508.24 and Sonic Frontiers Line 3 frontend with all balanced ics.
I did own the MCS1 and LR3s, sold both, and have re-integrated my two channel and HT systems. To switch between HT and Music, I just switch to balanced input on the Omicron, take down the screen, and move the center channel out of the way.
If you like the way your CA301 drives/drove your CS3.6s, then you'll be fine with either the CS6 or CS7.2. That isn't to say you won't hear a difference with more current and power. In the Thiel line the CS7.2s are the most complete sounding speaker. The driver integration is very good, it has the best transition from bass to mids, midrange is excellent, and it is not as bright as other Thiels.
Three MCS1s up front is a nice setup. Going with either the CS6 or CS7.2 would certainly enhance music playback, for both cds and movies, and may add more oomph. I think you would loose some of the seamlessness left<->right that 3 MCS1s provide.