Yeah, I'd hold onto the M81. I might pick another one up at some point.
That's what I'm looking to do.I use the Ampeg Classic. Love the tone and how it plays with other pedals (not counting OD, since preamps talk to each other--working on signal chain adjustments to see if that helps.) As far as DI goes, I haven't done this yet (no gigs due to COVID) but the plan is to use a transparent DI like the Radial PRO48. Tone-wise, I'd be getting the Ampeg and a non-EQed DI to FOH. FWIW, YMMV, etc.
I have an Ampeg Classic on the way from CA.
I'll use that and the transparent DI from my M81 if I need it.