Jamie, Sounds like a deal! I'll keep you posted
Spent about an hour messing with preamp tubes today left the amp settings neutral, bass 6 treble 6 (that's all I got)
Here's what I tried out:
12AX7's
60's GE long plates: Very balanced, clear tone not as complex as the mullard(not reissue) I had in there at one point but still very good. I put this one first because it is really what I consider the middle ground on everything I tested.
RCA 7025: Again nicely balanced like the GE but noticeably brighter, which I really liked, this one ended up in V1. It was a tough choice between this and the GE. The GE landed V2 and I jumper the inputs so it still lends it's tonal flavor.
Realistic(Japan): I had two of these tubes one had 4 seams on the top glass indicating it was from the <censored word> plant(set up by Mullard) the other had two seams and the plate structure was slightly different. Both tubes sounded excellent and I'd have loved to keep them in there but unfortunately both were noisy. It would cut in and out and after several tests it only happened with those two tubes, real shame.
JAN GE 5751: I bought this a while ago and have never really bonded with it in my amp. It's a much darker sounding tube, than anything I've tried. Not in a bad way, but it just doesn't fit my tastes. I think in a different amp that is maybe a bit shrill it would be fantastic.
Tung-sol Reissue: Not a bad option for new production, a lot better sounding than what most amps come with stock. It's musical sounding but a bit unbalanced. Highs can get harsh and lows a little boom-y but remember I left the amp at a neutral setting, I'm sure with some tweaking of the amp's eq I could have found a decent balance.
Electro-Harmonix: Made in the same factory as the Tung-sol RI. Plate structures are very similar, if not identical, only differences I noticed were a slightly different coating on the plates and a different getter. Despite those differences they sound remarkable similar with the EH being a little darker than the Tung-sol RI. I was pleased to see that these new production tubes could hang with the "Old Stock". Were they as good, no, but they were not so bad that it would warrant going out and spending 6-8 times as much on NOS.
12AT7's
Mullard CV4024: I bought this one, it was still what I consider reasonable and it's a tube that will hopefully last a very long time. Great sounding tube in the PI, blows away the sovtek that was in there. More musical, more detail great balance, just adds a nice lively-ness to the amp.
Unknown: just got this in my purchase the other day, still haven't figured out who makes it since most of the writing/symbols are gone. The plate structure is odd, it looks very much like a normal at7 but one end on each plate has depth to it with three holes punched in the plate, rather than being crimped flat. Whatever it is, it is every bit as wonderful as the Mullard. I had a hard time choosing between the two but I stuck with the Mullard. It had the tiniest bit more harmonics, it would be in-perceivable if I weren't sitting in front of the speaker in a closed room. I'll update when I figure out what it is.
Final configuration V1: RCA 7025 V2: GE long plate V3: GE long plate PI: Mullard CV4024
So that's it so far, power tubes are next but that requires re-biasing so it may take me a while. I may just swap them around, if they don't red plate it's fine
-Dave
*Disclaimer: These are just my thoughts from what I tried with my rig. You may get different results with your own rig. I play loud music in a band so my ability to pick out certain intricacies may be compromised. In short YMMV 
, tung-sol reissue, a mullard, GE longplates, JAN GE 5751.
