Tavish Vintage on the way - Tubes?


My Tavish Vintage Phono Preamp is on the way.
Can one of you tell me which tube has the most influence on the sound?
The input is furthest to the right and needs to be the most quiet....I understand...
What's the function of the other two? And, should they be matched? 
Any owners using any specific NOS tubes they like?
I have some nice Sylvania 6SL7WGT's that should be pretty sweet.
Thanks for your input.
budburma