Don't discount the PVA series amps from Anthem. Super clean and it will drive the 804's without any issues. Only omission is lack of balanced inputs, but if that's not a must, you can pick one up really inexpensive and I bet you'll be pleasantly surprised. It's definitely a "hidden bargain" in the amplification world.
Best used five-channel amp?
I'm looking to upgrade my trusty Primare A30.5 amp to something a little more muscular a higher end. I have a Classe Sigma-SSP processor and B&W 804s units for the front and an HTM3s for the center. Does anyone have recommendations for used units? I've been thinking about the Classe CAV 500 or the Theta Dreadnaught. I'd like to keep it under $4,500 or so. Thanks!