What is the best SS used amp for $1k or less?

Without knowing what speakers the amp would be driving, I don't think we can really offer you much help.

The best ss amp for you would be the Belles 150a hotrod based on your preference. Lots of good things being said about the vincent hybrid but the tubes are hard wired. That could be a PITA.

Look for a Parasound A21 at $1100 - $1200. They pop up now and again. The A21 is a KILLER amp that takes on the character of what's driving it. I use mine with a simple tubed preamp and it's glorious.

P.S. 250w per channel into 8ohms.

Unsound is correct. without knowledge of your speakers, advice you seek is suspect. For instance, I've had a Belles 150 Hot Rod and it was mediocre at best when paired with Maggie 1.6qrs. I'm sure it warranted the good reviews it got with other speakers. There's no such thing as "best," it's always system dependent.

Don't worry too much about your choice of amp: it would take a real bad one to screw things up. A properly built amplifier, with an electronics design that has stood the test of time, will have less relevance to the presentation of music than your speakers.