I had the Phi 300.1, Quickie V-4's in SE and another pair in balanced all on the Vandersteen 5A's. I have owned two of Vac's KT-88 amps, the other being the Standard 220 Signature. IMHO, the Vac's are not warm for a tube amp. Not in any of my setups anyway. I have heard their Renaissance amps, and that amp has more of a classic tube sound. They are both very good amps, so it comes down to synergy. I think think the V-4's were a very nice match with the 5's. If it were me, I would go with the Quicksilver's, simply because of synergy. The Nines are waaay easier to drive than the 5's, so keep this in mind as well. If your room is on the small/medium, V4's should be enough. I would not use any less than the V-4, power wise. Just noticed your price range. Grab the V-4's if your room is not too big. Great support, easy to resell if you don't like them.