I think a critical component to add to most SansAmp products is a compressor. It fills out the response, and it adds a little extra "give" (like a spongier speaker response).
The compressor itself doesn't have to be fancy. I'm using a Maxon CP101 in front, and it sounds great with every SansAmp I have (original, TRI-AC, BassDriver). For clean sounds, it adds a little cushion so the input signal doesn't crap out the SansAmp original.