amp for vandersteen Quatro maybe vandersteen 5a

Try to audition Rogue tube gear if you can. I use a pair of M-180 amps. Very natural sound and easy maintenance.

I agree with trying Rogue. Their amps, even the less expensive integrateds, are real giant killers. I listened to a pair of Vandersteen Quatro CT's with the Rogue mono tube amps and the sound was stellar. Prefer them to the Devalet SS amp. Also the Vandy carbon tweeter is a huge step up to the standard ceramic coated one. IMO.

Yup, what everyone said:
Ayre
ARC
(I assume Aesthetix is also a good choice as Vandersteen has paired with this at several shows)

Yes, I've heard the upper end Vandy's with all the gear you are listing and they all sound great. Heck, the AR Ref 75 with AR pre was about as good as it gets one of the times I heard the 5A CT. It just was musical, dynamic, detalied without anything getting in the way. I probably posted that above in this thread, but it's still that good in my head. All of us who were listening couldn't belive it was a 75 watt amp doing that.

The main portion of the 5A is tube friendly- most of our customers use our MA-1s on there to good effect.