"But for lots of bass players the amp is just a monitor. They want it to add zero color. In which case a DI is enough."
Guilty as charged. Decently fresh strings, my pick, the way I play & and a rig that is not broken and has sufficient headroom (it doesn't even have to be my own one, I'll gladly play over someone else's). Bass setting between 3 and 6 o'clock, mids between 12 and 2 o'clock, treble/presence again between 3 and 6 o'clock on any amp. That's all I need. No preamp. I don't even really have a preferred bass. And I still sound so much "Uwe" over each and every amp I play it is sometimes pitiful/laughable. (That said, I
don't like to hear my bass over the monitors, possibly just because I like to hear my bass sound coming from behind and not from upfront.)
When I read about your discerning and particular tastes in amps and preamps, I always feel terribly inadequate and wonder what is wrong with me. I have never been attached to amps. And in my 44 years of bass playing I've only owned about ten of them (Dynacord, H&H, Reußenzehn Mk I, Yamaha, Reußenzehn Mk II, Ashdown JAE Sig, Ampeg SVT, Roland, Markbass and Orange).
Come to think of it, speakers are more important to me than amps. I frown at rigs that don't have at least one 15" inch speaker, I even coupled my Ampeg "refrigerator" with a 1x18" subwoofer (from Ampeg as well) because the sub-lows of the 810 left me unconvinced. I've never seen anybody else do that, but the gain in oomph was marked.
Currently, I play 1x15", 2x12" (or 2x2x12" to be exact as two speakers are packed behind the other two) and 2x10" speakers. I've downsized. My peak was 2x18", 1x15" and 4x10" with occasional addition of a 1x or 2x12" mid bin(s). That offered reliable headroom and moved some air.
You didn't even need to turn it up loud. You simply were EVERYWHERE when you played over it. I know it's against the trend of the times, but I don't like to stand in the 'sound tunnel' of a comparatively small speaker cone area blaring at me (like many guitarists do), I like to be immersed in a (not too loud) indirect sound all around me.