Agree with stevecham, use the stock ones for a while before you start tube rolling. Keith Herron, when he gave us a demo at an NJAS meeting, felt pretty strongly that there should be no need to change the ones he chose. If you do decide to try different tubes, I always prefer Telefunkens, but I like their sound and their longevity. You'll need to ask yourself what about the sound you want to change, then go from there (an excellent source for that kind of information is Andy Bouwman at Vintage Tube Services).
