The prices of NOS are somewhat more, and I am certainly no rich man, but the $ difference might equate to a pack of strings or two, and while strings will stay new for two or three nights on the outside, your preamp tubes will be a more or less permanent main component of your tone that should last for as long as you own the amp. Start slowly, go one socket at a time beginning with the all-important V1. It can take a tiresome amount of switching tubes in and out of all the sockets ("OK, what did that first one sound like again?"), but when you hit on the right tube in the right socket, it's just amazing.
Check out the salvage bins that some repair shops keep around! $1 tubes, anyone? It's amazing that some people routinely retube their whole amp including all the preamp tubes, which probably don't need replacing. Probably some bum ones in there, but I have definitely found some 12ax7 and 12at7 beauties for $1 apiece!
For power tubes, which are pricier and in my case need to be replaced close to once a year, I use the economical and easy Mesa 430's.