Nice! I plan on removing the 2nd cat sometime soon (leaky flange near it), and may add in a slightly larger resonator. Since the main cat is the only one with a sensor on it, the other 2 can get chopped off and won't cause a CEL. Hoping for a smidge more sound, and to get rid of that high-rpm "die out" that you speak of.
A resonator should help in the "deepness" department. Just a straight through perforated core design should do the trick.
Any pics of the new setup?