Best Class A Amp under $2,000 used?

There's a Plinius SA250 mk. IV for sale here now near your price range.  250W class A power and has a switch between A/AB operation so can operate at higher efficiency and less hot for non-critical listening.  Best of luck. 

It's pretty clear that the original poster has no idea what he's doing. But for the others:

Yamaha B-1. 1975-1978. Caused Levinson, Pass, and others to dream into the future. 150 watts pure and only Class A into 8 ohms at .1% distortion, more than 250 watts at 1% clipping criteria. Nearly doubled down like a perfect voltage source ( 4 ohms ~ 500 watts at clipping) . Mega SIT VFET's, super quick with 72 nanosecond rise time. I've seen a few sell for $2k or so but often need work. 

Very rare. Only about 50 made, I had a couple and wish I had never sold them. Specified as 4-16 ohm load capable, but I successfully drove the original Martin Logan CLX prototype- which was nearly impossible and only one cut above a short circuit (production models were tamed down considerably but never sounded as good). Also superb on Stax ELS-8x's, another rare and difficult speaker needing lots of power and load stability.

Issue here is if you blow a SIT, they aren't available anymore. New SIT's manufactured by Digital Do Main out of Tokoyo might work, but I don't know if you can buy them.    osobagary@gmail.com

I got hooked and had to add my opinion.  I know the original question was what is best for under $2000, but bear with me me.  I am an electrical engineer, but i am not going to get into anything technical here.  I started out with tube amplifiers.  I grew up in that time when everyone wanted to get rid of their tube amplifiers and get the new better sounding transistor systems.  As a poor teenager, i bought used tube equipment for cheap (this was the 70's)  I just recognized it sounded good and was cheap.  So that was my basis, I just wish I realized how valuable my Fisher 800C with wood case would become.  The Fisher broke and was replaced by a unfulfilling solid state pioneer amp.  I then acquired a  pair of  Heathkit tube WM5 mono-blocks.   Being an electrical engineer I wanted to move forward into present transistor technology and wanted to stop dinking with tubes.  I listened and listened, and finally settled on a PS audio 200C, it sounded great but build quality was not that great (I lusted after krell build quality, but the Krell class AB which I could afford didn't sound that good) ).  I then found my present class A amplifier, which I think is one of the best sounding budget SS amps I have heard, the Forte 1A a 50 WPC class A amplifier.  This amp does 100W at 4 ohm and 200W at 2 ohm.  It was not designed by Nelson Pass, but came out of his organization and is very minimalist and just as well is his design.

Your speakers are 4 ohm, so with a Forte 1A you will get 100W which should be more than enough for your 88 db/w speakers.  you can find a Forte 1A for ~$500, I liked mine so much, I bought a spare for backup. 

So I think you are on target looking for a class A amp.  Generally it is easier to build a good sounding class A amplifier than a good sounding class AB amplifier so my suggestion is to buy anything that is  pure class A >100W @ 4 ohms and you can't go wrong. 

Just be aware, some of these amps are going on 30 years old, and will be needing to be rebuilt.  My Caps were still good, but I had to replace all the trim pots due to wear/instability.