Agreed, less is more. A local shop that I really like has a sauce with a strong flavor and a nice tang. But it is also a fairly wet sauce. They don't use a lot of cheese, and I think that helps the sauce breathe. I find with my pies, that if I use too much cheese, I can end up with soupy cheese because the water in the sauce gets trapped and doesn't steam off.
For my tastes, I find that Sorrento/Galbani mozz with a bit of Frigo Parm wedge is spot on. I haven't tried other brands of parm wedges, but grating it fresh is definitely better than anything I've ever tried from a bag. Frigo is very cheap at $2.44 for a 5 ounce wedge.