Bigjoe, The type and brand of tubes does make a large difference in the sound of a pre amp (or any other tube devise) - no doubt. If I may suggest, most specific recommendations you will get when you ask on this forum will be for NOS tubes, and not without some good reason, however NOS tubes can be a minefield loaded with hype and expense. Depending on the tube involved and the requirements of your component new production tubes can be as good and always much cheaper. If you want to get an easy lesson in how tubes sound start with new production tubes, many of which are modelled after old production and the sound difference isn't huge if even extant.
I'm not familar with the tube requirements of your amp, but if it requires a 12AX7a you could try JJ/Teslas (modelled after Mullards) for a warmer tone, EH's for a brighter tone, and EI's (my favorites) for a neutral tone and clarity. If it requires 6DJ8's you can try JJ/Tesla's for a warm tone, 6h23EB's for a very quiet and neutral to cool tone (not really a new production tube but fairly cheap for NOS),Sovtek LPS (or EH)for a cool tone if you need a very quiet tube, EI's for a neutral tone and clarity. There are others out there as well, I just mention these as a starting point which will give you an idea about how you might wish to voice your pre-amp. Once you have that pinned down if you have the dough and desire you can more selectively research the NOS market.