Re: What makes a good jazz amp?
Literally anything will do. When I did mostly jazz gigs, I used to just call ahead and see if they had amps laying around rather than drag a huge amp halfway across the city. I've played gigs with tiny solid state amps (ZT Lunchbox, little Fender SS amps that I've forgotten the name of), I've played gigs with tube amps (Fender Hot Rod Deluxe, Deville, Deluxe Reissue, Virbolux, Twin). My favourite local jazz guitarist played with a Plexi clone for years and got one of the best clean tones I've ever heard, more recently he switched to the Mesa Mark 5:25 and sounds fantastic.
The funniest gig setup of my life, I called ahead and asked if they had a backline for me and the guy was like 'yeah we have some amps around', but when I showed up all he had was a Peavey 6505+ amp, so I dialed it in for a standard clean tone, rolled my tone knob off and went for it. It actually didn't sound half bad, because the cabinet had enough push to it's speakers to feel nice and punchy.
If I have a preference though, I hate the Jazz Chorus. They sound awful and tinny, I always had to run my tone knob and volume knob much lower to get the tone soft enough to mix well with other instruments. They sound great if you are in an 80s new wave band, but for straight up jazz I find them lacking. The Twin Reverb as well, while it can sound really warm and sweet, I've never been in a rehearsal space or jazz gig where I was allowed to turn it up enough to get there tonally.
My favourite amps that I have played gigs with were the Fender Hot Rod Deluxe (I'm convinced it's one of the best amps ever made at this point), the Fender Deluxe Reverb, the Supro Coronado (think a Deluxe Reverb with a much more complex midrange), and my Traynor YCV 50 Blue (which is honestly nothing special, I think you could get the same result with any EL34 clean amp, nice and dark with a strong midrange).