Killer used integrated for

👍👍👍 on Exposure. Just plain musical and fun!

Yamaha A-S500. Measures better than some amps costing 5X its retail price and sounds great.

I would look for an old tandberg integrated may pay a little more than 500 dollars but not much.

Another for Rega.Brio is great, or if you want to save a little more and are ok with larger size, the Rega Mira 3 line was really great (what I am currently running).  Not super powerful, but with Bookshelf monitor style, the integrated does great, can run a sub, run as a pre or just amp, remote control, and matches great with their CD player or DAC~r. 

Krell kav 300. It’s slightly more than $500 but definitely has a typical sound signature of Krell. It looks good too.