Although I myself haven't jumped on the tube wagon yet, a friend of mine who works for a speaker manufacturer and who has written numerous equipment reviews considers Art Audio amps to be among the best he's heard. I mention this because as a reviewer he's been in a position to hear just about everything out there. I think their top level amp is in the $6k to $7k range. As others have said, it's still a personal taste and equipment/room interaction thing so the final decision is up to your ears. Best of luck.
Tim
Tim