I have used Amperex, Sylvania, GE and RCA varieties in other tube gear (not 12BH7) and tend to gravitate towards the Amperex and Sylvania. Not sure if their characteristics are similar through various tube types, but would guess they might be. I think I am going to find some Sylvania's to try. If I come across GE or RCA that are a deal then I will pick them up. I see long plates and black plates are the ideal ones to pick up. Any more specifics I should watch out for?