I have a Monoprice 1/15W Stage Right amp with the stock Celection speaker. I've upgraded the reverb tank, but found little improvement. I've watched a few YT video's on mods to this amp, but none seem to really make a difference. Can anyone make a recommendation to upgrading mod for this amp that is worth the additional $ investment? I'd really like to improve the crunch sound - I"ve thought about buying a diff amp (Peavey Delta Blues, if I could find one) - but this amp really does so much for the money - I'd hate to throw money away just for marginal improvement. The Gain knob is close to worthless - I can get a decent distortion by cranking it all the way up, but it seems more like an on/off than a pot. Would it be worth it to change out the tubes? The Speaker? I don't want to throw money away for a tiny improvement (like I did for the reverb tank - but it was only $40). Thanks.