Just so you know, this forum is dedicated to the production of surround material - not the playback.
That seems a little harsh, griff!
I certainly have no issues with discussing -playback here - after all, getting the playback/monitoring system correct is a very large part of the equation. And certainly - to my mind - playback equates to monitoring, and as such comes under production too.
Doesn't it?
Anyway - the way I would approach this question would be to forget all about using surround power amps - unless they are pure Class A - and instead go for a high quality set of Active Monitors. This way you will get the amps matched to the monitors, and also obey the cardinal/golden rule - all 5 channels should be the same make & model of speaker/amplifier.
They should also be as close to full-range as possible.
What's your budget?