I ended up deleting the 3rd cat and stock resonator. I put a small straight through res where the stock one was, and a si/so magnaflow muffler at the rear. 2.25" piping all the way back. The sound is deep and mellow (when the damn heat shields aren't rattling), and seems like the car picked up a bit of top end, with no loss of low-end power.
The stock manifold/y-pipe design wont give you that "rumble" like the turbo or UEL header cars have, but it still sounds pretty nice.