Very best 5 ch amp to feed a complete PSB system

You might want to try a Bryston 5 channel 9STT. It sounds very good and has a 20 year warrenty. If you loose a channel all you do is remove the amp mod that's a problem and send it back, you still have 4 amps so you can still enjoy your system while you wait for the other to return.
I used 1 when I had 2 seperate systems, 1 for 2 channel music and 1 for movies.

I would have to agree with the NAD M25 as well. It is a great amp and a very good value. t

Disclaimer: (PSB Dealer here). We use three amps the majority of the time with the PSB Synchrony One system (Parasound, Bryston, NAD). Currently, with our Synchrony theater room I have the Parasound Halo A51 driving them. IMHO, this is an outstanding sounding combo. The other amps mentioned also do a fantastic job. Nothing beats a Bryston amp in the long run. I would seriously look there as well.

I tried using an Ice amp with these and I was not really impressed with it. I suppose it may have been the fault of my Onkyo SR-806 being used as a pre-pro, but it just did not sound all that great. I have since relinquished the amp and I am just using the receiver to power the Synchrony One towers and CC. To me, it sounds better...

I am still looking for that ultimate amp for them. Still trying to figure out what has more of an impact on them: the amp or the processor... hmmm...

You might try an old cal audio MCA 2500. They are slightly older, but can be had for a song here on Agon. They are big and heavy, and run hot, but you get some serious bang for the buck out of this beast.