VTL ST-150 MB-450

Hedgehog is correct, they have triode switching, and I believe even the newest version has auto-bias.

Weiserb,

I believe you're thinking of the now discontinued MB-250t amps. The 185s are tetrode/triode switchable.

MB-185's only run in tridode mode not the more powerful tetrode mode.

I would take a look at the MB-185s, as they have the Signature tranny as well. On the pre-owned market, however, they are only going to run about $1K less than a pre-owned pair of MB-450s.

Anyone else have an opinion?

Bea told me to go with the 450s because they have the signature transformers providing a better power supply. The Summits dip to 0.6 ohms at times. Even though they are efficient they still need an amp that can put out current.

I drove my Aerial 10t's with a St150 with great results, and they like to suck up power. But when I moved them to a larger room I lost my mind and bought the MB 450's. The 450s are similar to the 150s in sound but they have like an iron fist control of the speaker They can play at crazy sound levels and never sound stressed. I am stuck in the 70's with classic rock. I think they are a keeper for me. And the new model may make the deal on a used pair even sweeter.

Bea talked me out of the 150's as well for my 20.1's (I was going to buy a pair and bi-amp.) She felt I should get Sigfried's but they were out of my price range; I got a pair of 450's which I'm very happy with. Your speakers are about 6db more efficent which (to me) make the 150 very viable. However I only heard the 150 once and never directly compared it to the 450's (but their qualities seem very similar to me.)

Bea is known for recommending VTL's best amps and generally she gives good advice, but I'd leave the 150 on your short list - especially if you liked it before.