I'm guessing you are playing that DRRI at GC louder than you are playing your Princeton at home. I'm also guessing that you are looking for thicker/fatter clean tones, not overdrive. That's a frequency response thing. You can change your frequency response with a speaker swap, but that comes with a significant sunk cost and there's no way to tweak the results. I suggest you get an inexpensive graphic EQ pedal and push up your lows and mids. Might be all you need.