Quick update: Put on the 330ci exhaust with custom dual 2 1/4"piping. It sounds great - quiet when cruising, burble down low and when I open her up she sounds like a proper euro sports car (read: refined and a touch raspiness). Performance wise, there is definitely an increase in the upper rev range.
Conclusion - this mod was good, I'd do it again. Out of the mods I've done I'd rank this up there with the 3.38 diff swap and AFE CAI which were both great bang for your bucks mods.
That ends my mod list for this e46. I am now happy with it.