I would make the investment into some decent NOS or used vintage tubes. They are worth every penny. You can get really good deals at Ham Radio Fests. Most people there have lots of tubes so you can get a bunch of different brands/types and the tubes will be well taken care of. Preamp tubes in Ham radios are typically not abused and have plenty of life in them. You can also find a tester there and test the tubes you find.
As far as brands, NOS RCA 12AX7's are great, so are Sylvania 12AX7's. Mullards, Telefunkens, Tesla, and the Goldpin Radioshack 'Realistic Lifetime' tubes are very good as well. Depends on the tone you are looking for.
The best advice I can give you is to go out and buy a bunch of tubes and try them all out. brands and years and types don't really matter as much as how the tubes will sound in your setup. Trust your ears. Don't let anyone tell you what kind of tubes to buy and believe the hype.