Power requirements for Acoustat 2+2s

You shouldn't have any trouble driving the 2+2 with the VTL MB150. I have experience with Acoustat 8s driven with VTL Ichiban 200 watt monos, Acoustat Spectra 1100 driven with VTL Compact 100 monos and Acoustat 1+1 driven with VTL Ichiban, Levinson 23.5 and Acoustat TNT 200. The TNT 200 works incredibly well with Acoustat speakers. If you can find one buy it.

I used to own Acoustat 3's with the c mods and drove them fine with a Hafler 220, which if I remember was 100 watts per channel. The Hafler wasn't a great amp IMHO but it drove the stats to any level I desired.

I successfully ran a pair of 2+2s with Blue Medallion transformers with a pair of VTL Tiny Triodes ( newer version with 45 wpc in tetrode mode). Not too loud but up to the power limit, the sound was AMAZING. The TT 25s have a super deep stage and are very transparent. The MB 150s should have no issues with the 2+2s as long as you are not looking to have them at huge volume and dynamic swings. I am assuming the 150 monos are running either KT-90s or EL 34s? The later versions ( MB 175s) run the 6550c and will have an advantage in "PRAT" but not be a sweet in the mids.

Sweet speakers. I used to drive 2+2 medallions with ARC VTM200 monoblocks (6 6550C's / amp). They did the trick, sounded very good, but certainly were not overkill. It may come down to your room size and desired listening levels.