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?
I have a used parasound amp for my backs, though you never said how much power you need, Rotel, Parasound are both sold at very resonable cost, and since you are just using these for ambient sound mostly...I would not feel the need to go nuts over this choice...but far more are qualified than me to help you. Happy HT!

Pair of Outlaw Audio M200 monoblocs at @$300.00 tons of power, clean sound, auto signal on.
Second the Outlaw M200 mono blocks. I currently use 5 in my HT system, and have combined them with high end two channel amps in the past for center and surround duties. They are well built, run cool, and one of the better values out there. Acurus and Parasound offer used alternatives in the 325 - 500 range. Acurus A-100, A-150, Parasound hca1000a, etc. Depends on how much power you need, condition of the used amp, and whether paying a little more to get a warranty matters.
A used Carver TFM-42 or TFM-45 can be had for around $400-$500.

I had Infinity Kappa 7's for my rears when I had a home theater and they drove them nicely with plenty of power to spare. They are rated at 350 wpc @ 8 ohms and 500 wpc @ 4 ohms.
There is a nice Carver TFM35 FOR SALE NOW, I hear good things about that amp aswell.