Is a VTL ST-150 enough?

Triode amplification is addictive, but the price is less power out of the amp. I had several triode amps, including a set of VTL 185 monos which sounded about as you describe (in triode), and on a variety of speakers. In Tetrode there was lots of power, but who cares?
Cheapest way out is powered subs. The other plan is something like the VTL 250 monoblocks, or to change to much more efficient speakers.
Welcome to the triode fan club.

I had a ST-150 with my Aerial 10T's and they sounded great.
When I moved to a larger room I got the MB-450's and they sounded even better.

The V.A. PARSIFAL need a amp with quality watts (balls) to get out the tremendous bass they are capable of ....
You should go at least to the MB-450's if you want to stick with MBL
For the summun you could match NAGRA amp or LAMM HYBRID amp
just a suggestion ...

I'm a VTL ST150 user (disclaimer: I'm also a VTL dealer) and I can only have high praise for it. You should notice if the power is not enough, especially on how it control the low frequency. I've tried briefly the Triode option but I've preferred the Tetrode mode that, at least in my system, offer the best performance. I've also used the Nordost Frey as a complete cable loom (now I'm using TYR, and BTW, I'm a Nordost dealer too)and IMHO they matches very well.
I think too that VTL should have another stereo amp in between the ST150 and MB 185.

David Manley made his amps switchable to triode because, given a reasonable load, he thought they served the music better. If speakers sound better in tetrode than triode, I suggest that they would sound still better with a good solid state amplifier - like a CJ 2500A.
Speakers and amplifiers are literally made for each other. Most modern speaker designs are made assuming high current solid state amplifiers. High voltage devices like tubes do best when given loads that do not require gobs of current and steep filter curves. Electrostatics, on the other hand, are tough on solid state designs and, as they are high voltage devices, they were made for tubes.

High voltage devices? Do really know what u are. Talking about? seriously read transformer theory before you make statements like that! Tube need an output transformer so they can reduce the output voltage! Therefore, voltage in high voltage out low but current high to speaker just the same as conventional transistors.