I'm looking to get more oomhp and grind outta my SVT3-Pro. It's got the stock EXH tubes in the preamp right now. What I'd like is something that would break up at lower volumes a little better, or at least give me more growl (I love the Ampeg growl), which is why I say high gain... that's the term people have told me I'm looking for. Preamp Tubes: 3 x 12AX7 Driver Tubes: 1 x 12AX7, 1 x 12AU7 So that is five tubes, right? Which ones would I be swapping out to get higher gain, and what brands do you suggest? I'm not looking to spend a fortune here. Max of $150 or so for the whole set, as I really don't know a thing about tubes.