look for an older zapco (quite a few of the ref & studio series on ebay right now)
older ppi stuff (art series, sedona, powerclass, etc. )
arc audio (my new amp!.. the best shit ever)
i say search for any of the 5 above brands, and search for a price in yoru range with performance you need, but you probably wont go wrong, if its for a sub, go with an hcca 225, its a no brainer, excellent amp, highest rated for the longest time, and thats for a reason.. not cause of good marketing..
if ur lookin for a good amp thats easy to come buy though, if you are using ur amp for subs, then look for one of there d class amplifiers. There not really cheap there bout midpriced but the amp is seriously worth the money.