Of course, your ears will have to be the final judge, but I thought these might be helpful.
Preamp tube reviews: www.fbk.eur.nl/BIT/MHM/gear/preamptubes.html www.thetubestore.com/12ax7review.html
Output tube reviews: www.thetubestore.com/kt66reviews.html
The August 2008 Guitar Player Magazine has some reviews of output tube reissues.