I haven’t used the vtb201s, so I can’t make the comparison.
I have a F-1X and F-2B and I don’t see a whole lot of tonal difference between them, I can EQ the same tone from either one.
For comparison, I have just two set ups that I use: power amp with F-1X or F-2B (sometimes I’ll add an SF-2), or a Walter Woods amp for small and light, and I find that those cover my needs.
It sounds like you already have a lot of amps/preamps, so maybe think about whether you really need another, or are your needs covered with what you already have. Tough choice since Alembic stuff is so great, but something to consider.