6SN7GT and VT-231 from the same time period are the same tube. VT-231 is the military designation. You see it alot because from time-to-time the military auctions stuff in storage. If you are buying NOS/NIB 40's vintage 6SN7's it is probably easier to find VT-231's than it is to find 6SN7GT's.
IMO Brent Jesse has the most reasonable tube prices (with very good quality) of any online dealer. I have bought from Brent before and will do so again.
Bruce Wenger of BWS Consulting (search google) is probably the most service oriented dealer I know. He designs and mods tube gear and dacs but he also sells from his tube stash. Bruce always calls me a couple days after an order to make sure that I am pleased (no one else has ever done that) and if I bought two sets of tubes from him and found that I preferred one over the other he would let me trade in the less preferred set for something else (I've never taken him up on it though). If you buy something from Bruce you can be sure it is good. I told him once I wanted 4 pairs of NOS Sylvania VT-231 and he called me back later and said that he only had 3 NOS matched pairs that he could make and that any other matched pairs he had would be in used condition. Some other dealers would have been tempted to "MAKE" a pair just to get that extra sale, but not Bruce. Bruce's prices are not cheap, they are roughly on par with Bob Malecki of tubeseller.com.
I've bought from Bob before also and will do so again but he never has Sylvania VT-231's. Also Bob Malecki only has 6SN7's for sale, so no matter how much you like him you will have to go somewhere else for you power tubes and rectifiers.
IMO Brent Jesse has the most reasonable tube prices (with very good quality) of any online dealer. I have bought from Brent before and will do so again.
Bruce Wenger of BWS Consulting (search google) is probably the most service oriented dealer I know. He designs and mods tube gear and dacs but he also sells from his tube stash. Bruce always calls me a couple days after an order to make sure that I am pleased (no one else has ever done that) and if I bought two sets of tubes from him and found that I preferred one over the other he would let me trade in the less preferred set for something else (I've never taken him up on it though). If you buy something from Bruce you can be sure it is good. I told him once I wanted 4 pairs of NOS Sylvania VT-231 and he called me back later and said that he only had 3 NOS matched pairs that he could make and that any other matched pairs he had would be in used condition. Some other dealers would have been tempted to "MAKE" a pair just to get that extra sale, but not Bruce. Bruce's prices are not cheap, they are roughly on par with Bob Malecki of tubeseller.com.
I've bought from Bob before also and will do so again but he never has Sylvania VT-231's. Also Bob Malecki only has 6SN7's for sale, so no matter how much you like him you will have to go somewhere else for you power tubes and rectifiers.