For rollers - Best "low tube count" amp

I would like to get into rolling power amps. I have a preamp now that uses 2 6922 tubes, and I love trying different tubes. Thinking about going to HT, and setting up a 2 channel all tube sytem to roll tubes into.

What would be a good, ideally integrated, tube amp to roll different tubes into. I know Unison makes an int that uses two 6550's. I would like to find an amp that is highly musical, that I can try different tubes in to get to know the various NOS tube's charicteristics.

Most power amps us at least a pair per side, meaning I would have to buy 4 tubes+ to roll.

Any ideas on a great sounding int amp to roll?

Total output should be reasonable, but not the key factor, as I will buy speakers to match the amp (Ref 3a, silverline? etc)

Thanks!
Paul