An SVT is a midrange machine unless you intentionally dial in a scoop with the EQ or engage the Ultra-Lo switch (which engages a deep mid scoop). I haven't heard any clips of the Super Vintage that suggest it has a scoop built in (and it doesn't seem to offer the Ultra-Lo option found on most Ampegs). A B-15 and SVT should sound pretty similar set flat (both use a James-style tonestack for Bass/Treble that is mostly flat set at noon), though the B-15 cabinet obviously is a big part of its midrange-forward reputation.I don't think you'd like the SVT one, knowing your preferences. The Black Panel can get super dirty if you want, but it has the nice clean vintage amp sound too. There's no way you'd get a B15 sound out of the SVT one though. It's too "SVT scooped".
On the other hand, a Fender tonestack like the '64 utilizes has a mild slope mid-scoop at most settings- it's what gives bass amps with that kind of tonestack a generally clear but round tone (there is also a treble boost at most settings that can extend into the high-mids). The closest you can get to dialing out that middle-mid scoop is with Bass/Treble at zero and Mid cranked. The cabinets originally used with Bandmasters/Bassman amps with bass were pretty mid-centric and so you could probably balance out the spectrum to some degree using the cab-sim.
