I love my 1977 2203. It's a great sounding amp. But I couid wish it had more gain and sustain. It really does not do singing sustained notes very well. And that's with the hottest preamp tubes I can find for it. Even with a 20 db input boost via a Seymour Duncan pickup booster pedal. I just want it to have more drive. And yet I don't want to do any irreversible mods to it. No holes drilled. No added tube sockets. I also don't want to lose it's touch sensitivity, where it can go from clean to raging by a change in pick attack or turning the guitar's volume knob. So that places some serious constraints on what mods I'll allow to be done. Since I really don't have a lot of experience with various Marshall mods, personally, I'm asking for your opinion. Within the constraints I've set, what would YOU do to try to get more gain out of this amp? I do not expect to reach the kind of liquid smooth gain levels that would come with adding another tube and two gain stages. But there has to be something that will help.