These are the amps i've been using with a few empeg decks i've installed in mine and my friends cars.

I did a quick search on ebay, they are always on ebay. This is just to give you guys an idea.

A/D/S 4 channel
Going rate on ebay is around $50 for a brand new one

A/D/S 6 channel
Going rate on ebay is around $150 for a brand new one

Hope this might help you out a bit, i've had great luck with all of my a/d/s products.