I've had good luck with getting good tone out of most of the Peavey gear I've owned or gigged with, and I've owned and gigged through a number of different amps over the years. I have never found any attempt by Marshall at making a bass amp rig that I could like, let alone tolerate. I had the displeasure of gigging in a band where the backline was all Marshall provided by the band's leader/owner/etc. He wanted the unified look onstage. It was great for the guitars, but all of my basses sounded like muddy crap no matter what I did to try to e.q. things out. Oh well, at least it was a paycheck, and I didn't have to haul my own gear. I just haven't liked Marshall bass gear scince then.
Have you had a shot at the VBA400 and VBC cabs? One of the few good things marshall did for bass.
The old-ish Dynabass amps & cabs were pretty good too