I was going to say JMP-1 myself.
It's my favorite live set-up (a JMP-1 and the EL34 50/50).
It's such a classic crushing sound and you can easily get laid back rock and classic rock out of it.
I have three of them - 2 stock and 1 Voodoo Amps modded.
I'll never get rid of any of them
Big, big fan. I haven’t played one in a long time, but every record I’ve heard them on is just crushing. They are vastly underrated to me personally, and sound like nothing else Marshall does, albeit is 100 percent Marshall to the core though. I’m guessing it’s the passive EQ tonestack, this is a very uncommon thing to do in amps in general and I think it makes a difference in a killer way here. Basically, none of the controls interact like other amps, which creates unique sounds I think. Just an absolutely killer sounding pre.