I have no idea why people here don't just answer your question. There are a few very good class A amps to chose from. The best under $2,000 used? That's a hard question to answer because there is no best. It all depends on what kind of sound you are looking for. If you want a very detailed sound, try the older Krells, want a more musical sound, Thresholds, and if you like something in between, Mark Levinson. These older amps are still killer machines and would still be fine in a system today. I didn't put specific models because there is lots to chose from, so do your research on which model you like most. Good Luck!!!!!