Ok I know another tube question, but I wanted to know which 6550 I should go with. I just picked up an Ampeg SVT-300 power amp(the powewr section from the SVT-II) and it needs a retube. So i'm considering these tubes, Electro Harmonix 6550EH, Tung-Sol 6550, and NOS GE 6550A. I;m lookking for a really nice tube with a nice tight low end. So anybody got any opinions?