Solid 2-chanel amp to drive rear speakers?

I am nearing completion of a system that will be used for HT and music, having purchased an upgraded-Anthem AVM-20, an Amthem MCA-50, a Velodyne DD-15 sub, and Paradigm signature S-4s for the front, C-3 for the centre, S-2s for ths side and likely the signature dipoles for the rear for a full 7.1

I need a 2-channel amp for the dipoles and since I have just spent a lot of money (though mostly used through Audiogon) I would like to keep the budget down for a 2-channel amp for the rear speakers, knowing that if I want to upgrade down the road I can get a killer 2-channel amp for the fronts and use the MCA-50 for the rest.

I don't want to spend more than $500 or $600 and would prefer to spend less. What amps should I consider?