I have been thinking about trying out more tubes for my marshall (1967 100 watt plexi) I have been thinking about mullards, telefunken, tung sol, rca, GE, phillips for 12ax7's and or El34's. THe problem for me is, there are SO damn much to choose from, I really don't know which to settle on. I have flat plate tubes, long plate, short, ribbed etc. .....then there is the matter of model numbers. Some 12ax7 made by Mullard have very different numbers other than Ec83 etc.... The there are evilbay sellers selling a tube made by telefunken or mullard but with a different name. Last most tube sellers list the test results of a tube and then stating that it is very good..... the problem is all Ican do is agree because I don't what half of this stuff means..... People can you help a chap out?