joey54 poses the most important question.....Which speakers will you be using? Many excellent amps are recommended here. I have experienced and observed dismal results with mismatching amps and speakers more than a couple of times. Some amps sound great with some speakers and not so great with others.
Searching for a "killer amp" in the used market may not be the best path. Since you are looking to upgrade your "basement" system I infer that you may not be looking for a mega watt amp? But I don't know the size and geometry of your basement.
My course would be to audition possible amp candidates with YOUR speakers. That is more difficult in the used market. Or, read all the input from users on all the forums you can find and try to see if others with YOUR speakers have had good or bad results with different amps. Amp and speaker synergy can't be over stressed. Good luck.
