Audio Research Corporation ARC Reference 600

Another vote for the Ref 75's. They make the finest sound I have heard in my system. Detailed and dynamic, with good base slam, but no edge or harshness at all. They do not run hot at all. I am using them with sensitive Daedalus speakers and I have neighbors, so don't play at 100DB. I haven't been able to move the meters more than a micron, since I bought the amp. A proverbial no brainer if your speaker and music choice allow

You can get the same "hot rod" effect with a set of Ref 300s with half the cost and effort. Even the half power of the 300s is more than needed as others have already stated, but that doesn't seem to be your goal. I would have ARC go over the amps regardless of tube age. Just like a high performance engine these amps need an open check book to give their best and avoid costly repairs.

For the vintage, Ref 300 is superior in sound quality to Ref 600. Google for reviews and probably why Ref 300 are more $$ than Ref 600 in used market.

I am thinking about VTL MB 450 amps as well. It seems like ARC has more fans then VTL. Is there anyone who would choose VTL MB 450's over the ARC 300's?

Those speakers are so efficient that most often they're using only "fractions" of a single watt! You seem very enamored with the idea of ultra power amplifiers (hot rod effect).I say in that case satisfy your craving and go for it. It's a strange match but if it makes you happy, why not?