Best Class A Amp under $2,000 used?

Sorry, I missed seeing the first part of your post! Dali's/Wadia is a good speaker/source combination! I still recommend a SET tube amp (even one using 300B tubes). Very smooth and yet detailed enough to hear all the nuances in your favorite recordings!

I had a Forte 4A class A amp. Forte was built by Threshold. 50 wpc into 8 ohms and 100wpc into 4 ohms. All in Class A. They could handle Thiel 2.3's which I had at the time. When on the market they get scooped up quickly.

Sony TA-A1es integrated. 

Get a pair of clean efficient speakers and a good single ended tube amp as I recently did, and stop chasing watts…my current rig sounds better than anything I’ve had in my home in over 50 years of audio fun…it’s simply funner, and more dynamic somehow (everything I knew is wrong?). Watts SCHMATTS! Note I use a couple of powered REL subs for "under 40hz" duties so maybe I’m cheating a little…still…great sounding, more musical, and, dare I say, more realistic, is just a better thing to have as it’s better. Or as Hawaiians say, Mo Bettah.

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.