Nice used tube amp under $1000 used

Kind of a hard question to answer w/o knowing the the manufacturer & model, or at least efficency & impedence curve, of your speakers.

Also would help to know what type of music you listen to, how large your listening room, and how loud you like to listen.

In the under $1k range, you will likely have to go with older, classic, amps to get quality and dependability. But, there are a lot great older amps.

Cary definitely lays the midrange on thick and velvety. There's a 35wpc SLA-70 Sig for sale at $750

There's a pair of Quicksilver mini monos(25 wpc) at $635 right now. You can use a variety of output tubes - EL34, KT90, KT88, KT77, KT66, 6550 or 6L6 - to cater the sound to your liking. Quicksilver makes fantastic amps at affordable prices. (Quicksilver spec page). Here's also another pair for $750 w/ latest output transformers

Classic Dynaco mkIV monoblocks(40 wpc) could also be a good choice. These are basically the monoblock version of the famous ST-70. There's an upgraded pair for $800