The Grace is a good medium mass tonearm, the PS audio is probably a good step up still. I'd try a Dynavector, a Shelter, or an Ortofon. What's your price range?
moving coil vs. moving magnet question
As someone who is just getting back into the whole "audiophile" thing, I'm wondering what kind of cartridge to get. My Rega P3 with Grace 727 tonearm presently has an old Supex 900 low output moving coil cartridge that I'd like to replace. I use a PS audio step-up for it, but wonder whether I'd be disappointed if I went to a MM cartridge, e.g. a Shure V15v. What's the sonic difference between MC and MM?