Best Class A Amp under $2,000 used?

Might I suggest a different direction? 1) a pair of Crown PS-400s. ($700-$800 used) Heavily biased into class A, plenty of power,excellent specs,bullet-proof build quality, and sound pretty darn good! A Crown Macro or Studio Reference these got an A rating for sound quality from TAS,Stereophile and other audio mags, unreal power 760wpc-8ohms,1,100wpc-4ohms !
($1100-$1500 used) Best of all but hard to find for your price. Any of Jeff Rowland,s bigger amps.  They all sound great!

...he's not listening.

Perreaux PMF 1850. 170 watts of Mosfet power..  can't be beat for sound quality and will cost less than $1000.00. 

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!!!!!

+1 @nordicnorm