You can get an AVR/AVP with pre-amplifier outputs to pass the signal to power amps, and then out to the speakers. Any AVR/AVP will have decent to excellent DSP for all channels, depending on how much you want to spend.
For example, you could get a cheap (and I mean cheap) Onkyo AVR that will power all your speakers, but it will have the lease effective DSP (Accu-EQ, I believe). Pioneer Elite has MCACC, Yamaha has YPAO, Denpn/Marantz uses Audessey, Anthem uses ARC, and NAD, Arcam, etc use Dirac. ARC and Dirac DSP are considered the most powerful software, with Audessey not too far behind.
I am not an expert on power amps, but from what I have read, D-Sonic amps are pretty good at the power levels you are looking at. Just remember, that with every doubling of power, you gain 3dB in SPL. That adds up pretty fast once you get into the hundreds of Watts, since a perceived doubling of SPL is a 10dB gain.