Firstly, my current system is:
Marantz SR-4200 AV receiver, with 2 x floorstanding fronts, largeish centre, and bookshelf rears. All speakers are 4 ohm impedance, so I'm running 2 x Behringer EP1500 power amps, to power the fronts, center, and one rear. Oh, and a sub. All except the rears are from an Australian kit company, and I'm very happy with how they're already sounding. I can't post links yet, but they are theloudspeakerkit S250, F6 and C6
My next upgrade is looking to be the rears, as they're definitely the weak point in my setup. I'd like to move to the Emotiva ERD-1, since my rears are close to the back of the room. From what I'm reading, I'm going to get best results running both of them off a power amp. So I'm thinking of adding a Behringer A500 to run them, which will then "free" up one of the channels on an EP1500.
So my question is, what can I use the spare channel for? I could run the centre channel in bridged mode, but that seems like overkill. Or I could run the subwoofer off the Behringer instead of using it's plate amp, but will going from 250W to about 400 make that much difference in reality? Or do I get something like an Emotiva XPA-3 to run the centre and rears, and use the Behringers in bridged mode on the mains?
Also, note that due to my room layout, 7.1 wouldn't really work, so it's 5.1 for the forseeable future.