I recently heard the latest V4s with Kt150 tubes in an unfamiliar system set-up by a local dealer and it was just amazing to everyone present. I think that is a first for our audio group.:) While I've always admired Quicksilver and felt they were excellent at the price point and beyond, what I heard was WELL beyond my previous experience with the Quicksilver lineup and what I was expecting to hear. This aside from listening to an unfamiliar system. Power, tonality, harmonic resolution, simply put a very natural and believable presentation on all types of primarily acoustic music including small ensemble jazz, choral, piano, solo voice and orchestral.
You made a great purchase and if you REALLY want to hear what that amp is capable of I would say go for it, I don't think you'll be disappointed providing there aren't significant changes to the transformer from your V4's to the latest, only Mike Sanders can fill you in on that. I am planning on auditioning the latest Silver 88s with the 150s to see if some of that magic carries over in my system.