You're right about tube prices, and obviously not just the ones we've mentioned. This hobby could get real 'pensive over the next few years. Vintage tubes - just forget about them. Everytime I go to an auction/flea market/yard sale, I look for old radios - just for the tubes. I just recently picked up a couple of console radios from the 50s for $10; both have 6V6 PP amps. One has a couple of TungSol 12AX7s, which are easily worth more than what I paid.If you can bias each tube in your amp, I'd just get a single Wing/C and be done with it. Thanks for mentioning the failure. I purchased a matched quad about a year ago for my Cayin. I'll have to keep an eye one them.
Guinevere is in need of serious repair. I was never very happy with the copper chassis. I used copper that was too thin and it's pretty microphonic. I can tap the top plate and hear the ringing. Also, the last time it was running I lost a ground somewhere and heard nothing but 120Hz buzzing.
About 6 months ago I picked up a deHavilland Verve and a Yamamoto A-08S. It's a very nice combination, so I'm not real pushed to fix Guinevere any time soon.....