Which Preamp

I'm thinking of trying a preamp/power amp combo to power my Bergie 115/210 cabs. Power amps under consideration are QSC 3402 or the Stuart World 2.1. QSC because of power/weight/reliability, Stuart because of power/weight/reputation for being a good sound for bass.

I once had a Demeter HBP-1/Hafler setup. I thought it sounded a little thin. I'm wondering if the VTBP-201S is fatter. I hear its EQ is rather subtle.

TBer Mission:
Tell me about your experiences using/comparing the various high quality preamps on the market. I'm looking for fat AND clear bass with sweet midrange. I don't slap much, so sparkly treble is not my thing. I like the warm smooth mids of tubes, but want clarity in the low end. And lots of low end too. I want it all. Under consideration are:

Kern IP-777 (never heard this one, BP reviewed it as as having a clear but fatter than Demeter vibe, and more hifi than Alembic FX1 (which I thought sounded raw and unrefined). This one intrigues me the most right now.

Demeter VTBP 201S

Aguilar DB659 (a bit "fuzzy" I thought).

Ashdown RPM-1 (I'm currently using an EVO 500 head which I like overall, but its a bit compressed amd mushy in the lower frequencies. It may be that power amp is not powerful enough for the Bergies).

Others?