Ive read alot about NOS vs the Current Production market, but im not sure what to do here. I have Two-Rock Custom Reverb Artist 100 watter with 4 6L6WGB and 5 12AX7's. I know the guy in Connecticut that runs Telefunken USA and i was gunna get the preamp tubes from him, but im not sure what to do. I hear that the Groove tubes are made on old GE equippment, but do they compare or sound like the real deal? How about Sovtek or Svetlana? Im very curious. I hear tons of great things about NOS JAN Phillips 6L6 tubes, and great things about Mullard/Amperex/RCA/Telefunken. I currently have TAD's in the poweramp and no name chinese in the preamp that the amp came with, and it sounds great, but can it be better? Please help me out, and i also have no idea how to bias my amp. I have a voltmeter, but i need help! Thanks!