I've had my Traynor YBA-1 for long enough now to say it's probably the best amp I owned, at least for me, for the kinda stuff I like to play these days.
It's in the vintage-y Marshall ballpark I'd say, but it's still its own thing. Looks cool, build like a tank, costs a fration of a Marshall branded point-to-point alternative from that era.
Does glassy cleans until you turn it up, with the volume control around noon it starts growling. Not even in a crunchy sorta way, your notes and chords just start to sound pissed off and bloomy and full...if that makes any sense
The key is to push the front end with something like a microamp. That's what I use, but I'm sure any klon/lpb-1/sho/etc would work as well.
Or just run yer favorite dirt box in front of it, it takes all pedals like a mother. Singe channel, no master volume, no fx loop...and enough low end to be used as a sonic wheapon.
Still though, if the sort of hardcore you're into needs a chug-worthy responsive amp that doens't have the plexi-esque spongyness...you might want to look into the mesa mark series or something
I get what you say about the Marshall jcm series. Awesome for a lot of styles, but that extremely compressed overdrive just isn't for everyone.
Fwiw, if I needed a back-up or replacement for my Traynor, I'd check out the Victory Sheriff 44. Pricey, but probably better build and still cheaper as the current Marshall equivalent.