Note …. you cannot change and overwrite the 16 presets on the left hand model knob. Herein lies the problem. You need to change your presets and store them in the user banks (the channels). This is where you can lower the channel volumes to equate different presets. At this point (as Line6Drew pointed out) you can lower the channel volume and then run the Master Volume higher. However, make sure you understand, that IF you are running the Master volume high, DO NOT select any of the Amp Models via the left hand knob or you will make yourself and everyone else within proximity deaf. You may even break windows? I am sure this is a HUGE problem for the retail stores when unknowing folks try these amps out …. ouch. I never understood why Line 6 made the presets so loud to begin with? This is also why I never let anyone try my Spiders without being there to oversee what they are doing or else (as per Murphy's Law) they will crank the master and select a model on the left hand knob !~! Also, many of the stock channel presets provided by Line 6 are also very loud to begin with. This is why users need to go through the amp and average out the channel volumes of everything for comparison and also (if desired) to eek out more usable Master Volume level. However, as stated before, once you crank up that master volume, you are always in dangerous territory with the left hand model knob should it ever be activated. I think in essence this is a very bad design flaw by Line 6 on the Spiders, but it is what it is. Again, I reiterate, it can be dangerous for unknowing people to try your Spider amp without you overseeing what they are doing.
Hope this helps?