Best used amp in the $1500 range

One to consider in your price range would be the Ayre V-3x.

For my taste and budget, I am quite happy with my BAT VK200.

I would be looking into a Parasound A21. You could find one for under $1,500 used. 250 watts, 60 amps peak current per channel will be more than enough power.

I personally like McCormack amps.
My current amp is DNA-225, which you can probably get somewhere around your price range, but prior to that I had DNA-0.5 Deluxe and DNA-125. All are excellent amps.
Upgrades from SMc Audio are possible if you ever decide to improve it.

There are a number of good choices in your price range; which one you choose depends largely on your personal preference, speakers, and rest of components.

In addition to the McCormack, Parasound, and Bryston suggestions above, I would also recommend a Pass X-150, Monarchy SE-100's, or one of Marsh's offerings. If you have electrostatic or planar speakers, then consider the InnerSound ESL-300 (which I own).

Michael