Hey Dante,
It sounds like you found the problem, at least I hope that was it. That's really a shame though about the R-2's.
I remember in the old Forum, I posted a full review of those tubes in the Classic because I loved how they enhanced the low mids and bass response in my Classics, without making the top end too crisp or brittle. Ever since FMIC bought out Groove Tubes, The whole product line has suffered IMHO. It appears they only focus on the tubes they want for the Fender line and associated brands, and let the QC on the rest of the line go to pot. Like you, the last go around I had with the R-2's didn't fare well for too long either, as they were short-lived, and gave similar results to my amp systems as well.
So, the quest goes on for the right tube for the Classic. While I love how the Mullard RI's respond in the MP-2, I'm not sure I would like them in the Classic. The Mullards enhance the upper midrange frequencies as well as the low end, and that's something I don't need in the Classic. That preamp seems to be closer to a Marshall Plexi type tone than anything else, and like a Marshall, it needs help with the low end. I think if I get on the horn with Doug, at Doug's Tubes, I might be able to find what I'm looking for in his stock. ( He likes all of us at the Depot BTW
)
I'm glad you got the problem out of the way. Now you can strap on your fake beard, and go do the Tube Steak Boogie all night long
Harley