Re: GO-NAD!
I've done quite a bit of tube rolling with this amp, and I found that your best bet is a Tung-Sol in V1 (of course tested for high gain and low noise), a Ruby 12AX7AC5 HG+ in V2, which I requested to be tested the same way. I find that the clarity of Tung-Sols in V1 make a world of difference, and nothing else really matches it. For the record, I went through JJs, a Mullard RI, a couple EHX, a couple Sovteks, and several Tung-Sols.
For a while, I thought Tung-Sol in both V1 and V2, but I found that V2 needs to roll off just a bit of high end to tame the amp. It's pretty bright all in all, and you can get some sizzle back with the presence knob. If you don't want to dole out for the Chinese or if you don't like Chinese tubes (and I could see why you wouldn't after the garbage that comes stock in that amp), then give the JJ ECC803S a shot. It's the long-plate design, and it sounds much, much better to my ears than the ECC83.
The PI deserves its own paragraph. A lot of people say to use a Sovtek LPS in the PI slot. I tried that, and it works fine, but the amp was a bit compressed, and unpleasantly so. I tried the Mullard RI there too, and it smoothed things out too much, and you could really tell the power section was being driven hard. Finally, glassman recommended I put a 12AU7 in that spot, and it was like magic. The amp opened up, the clarity returned, the preamp crunch was still there, and all was right with the world.
As far as power tubes go, I just bought a pair of JJs, biased them up properly around 70% of plate dissipation, and called it a day. I messed a little bit with the bias, cooling it off, heating it up, etc., and it's been so long since I did it, I couldn't give you the milliamp reading, but I do remember that it came right back to my 70% calculation.
I could talk all day about the tubes I've put in this amp and the results I've had, but my bottom line recommendation is Tung-Sol -> Ruby 12AX7AC5 HG+ -> 12AU7 (cheap JJ works fine, select it for low noise) -> pair of JJ EL84s. Good luck, and feel free to ask me any questions. I'd be glad to help and do my best to answer.