amp for vandersteens

Steve Mccormark mentioned before in the forums that people who own Vandersteen speakers report that the Mccormack amps can make them sing and perform as if they were made for each other. However they are increasingly becoming hard to find, but not impossible, especially ones with the upgrades.

Audioresearch!

Second the post above - Audio Research tube amp should be strongly considered.  Buy the best newest one you can afford.  Older ones are fine too if you are on a tight budget.  Vandy's need a little 'waking up' in my experience as they are voiced on the smoother side of the spectrum.  ARC amps will give you the tube magic but don't roll off much at the high end.

I had incredible success driving a pair with a Theta Dreadnaught 1 vertically biamped.  It’ll be hard to find the pig-tailed cabling to do this now.   I don’t think you can go wrong with Ayre, Theta Dreadnaught (First gen only), Quicksilver, McCormack etc.  
I currently drive my 5A’s with a pair of Theta Citadel 1.5’s and love them.  

Buy an old Counterpoint SA-100 that can always be upgraded to sound fantastic.  In stock form I used one to power my Vandersteen model 5s.  The sound blew most people away.  Used one just sold on ebay for $210.

Happy Listening.