OK, tube freaks, where are you all? I have to replace two of the KT88s in my Trace Elliot V6. Of course, Ideally, I'd replace all 6 of them at once, but as 4 of them are OK, would it be a major hugey to just replace the two bad ones for now? Financial considerations, you understand. There doesn't seem to be any sort of bias adjustment on the amp. Also, are there huge differences in the different brands of KT88s? I have found some websites where people actually argue about the Electro Harmonix ones VS. Czech Republoc and Chinese ones, but they seem to be audiophile stereo freaks rather than bass amp freaks. Will the brand make a discernable difference in the tone? There definitely seems to be a pretty wide range of prices. opinions, please. I yield to your expertise.