Amp to drive my AR-90s


I've heard differing opinions on how many watts per channel I need. What do you suggest to drive my 4-ohm AR-90s?

If I want to stay under/around $500. What used models should I be looking at?
dtotheatothevtothee
I am looking at picking up a used Adcom GFA-555 once I get my speakers fixed. 300 wpc into 4 ohms from what I've read...
I ended up with a GFA-555mkII and a GFP-750 preamp. I've got all the speakers refoamed but one of the 8" is rubbing.

I'm thinking the spider might be gone on that one...look for a replacement now.