I am currently planning out my exhaust as well (thank you bonus)

Basically the following:
-Join the 2 2.25" pipes before the second (redundant) cats
-the Y pipe will go from 2.25 inch for the 2 inlets to an outlet of 2.5"
-add a Flowmaster Super HP-2 (18" long body, 2.5" in/out) right after Y pipe Link
-straighter route to rear
-another Y pipe (2.5" in to double 2.25")
-2x louvered bullet mufflers/resonators Link

I decided against a full dual because on weight and no real power gains (since our headers seem to be the real log jam in our exhaust)