Best used mixer for under $500

Hi! I recently started DJing vinyl at a few venues, usually I use the venue's turntable/mixer gear. but i want to buy my own set up so that i can play more venues.

what is a good mixer that i can find used for under or around $500? I see a lot of the older pioneer mixers (DJM 400/DJM 500) for $200-300, but it sounds like they have pretty bad sound quality. Having four channels would be nice, but not a requirement.

What pioneer models have consistently good sound quality? What about the Denon or Rane mixers? Or are there any other brands/models I should be looking at?

Thank you!!

Also would you buy a used mixer, sight-unseen (e.g. on eBay)? I know some of the older mixers can have a lot of wear and tear, especially if they were in a club. What signs do you look for to make sure the mixer is in good condition?

I have a Denon DNX-1100 for sale for $300 (free shipping anywhere within continental USA). The mixer is in mint condition.

You can buy a DN-X1600 for that, loved it to death until the built in scratch-certified soundcard stopped working with recent versions of Mac OS.

i picked up a djm600 for $300 and it has 1 scratch on it. very minimal signs of wear. and i love it for the price