Rack preamps are tough finds these days... I'm still hoping (but not holding my breath) that Mesa would release the Subway preamps in a rack format, or at least a format that fits on top of my Subway D-800+. All the flavors, one power amp.
How much do you lean into one component for your sound? I lean very little into my preamps the majority of the time. Bass into DI and done. Even when I use my preamps, I'm not a huge knob tweaker, a little here or there unless I need something radically different. I have no problem with studio/live gear, but you may not. EQs built for bass amps aren't inherently different, they are just voiced at specific points. A studio style channel strip may have less bass friendly EQ centers.
If you want to go down the pre/power rack path, here's some more information:
The Ampeg SVP-Pro is a nice unit; I still have mine. It's fairly flat frequency response wise with all knobs at noon and lots of tweaking ability. The XLR in pre-eq config, is taken at the beginning of V1 so the gain staging for both FoH and your amp start there. There is some pleasant saturation to be had at that first gain stage, but again it goes to FoH as well. If you tweak the first gain knob mid show, the sound man will be looking at you funny. The drive knob is an upper mid grind which also needs a bit of low compensation. The unbalanced line out brings the last of 5 tubes into action. I special ordered mine in the 90's and haven't seen another in the wild. My most gigged preamp and very flexible but there are reports of noisy samples.
BBE BMax Solid State - Still have one. The XLR is the Achilles heel, post-eq only. The Fender tone stack can get to flat, but little tweaks of the knobs make big moves. There are threads floating with the designer (Judd Levinson? I think) who describe design goals of a big bottom like the Alembic F1-X and the bright top like a Glockenklang. Something like that anyway. I never used the tube version. Dry/Clean sounding, fast transients, a very immediate sound. Ed Friedland, the Bass Whisperer, had one in his YouTube videos for a while when presenting various basses.
GK 2001-RBP - I had two that were unreliable. I didn't attempt to trust a third.
SWR Grand Prix - I miss it for nostalgias sake, but I think I get pretty close with the BBE Bmax. Not particularly tube-y like the Ampeg. At the right price, I would buy one to see how good my memory is.
Trace Elliot GP7 Preamp - Wasn't a fan, moved on quickly. Briefly ran one bass on the TE and another into the SWR.
All that said, if I'm jamming with someone, the Mesa D800+ is going with me, and the rack gear stays home.
(but if you see a mic in front of the speaker, you might actually be hearing the amp).
That is too funny, I didn't notice that when I copy/pasted this morning (Learning Moment)
