A turbo'd 3400 sounds like fun. I don't have the cash for something like that though.
My plan is to do a single-piece, mandrel bent, stainless steel catback (2.25 inch?) and terminate into two Super 40s (or 44s... I'm not sure what the difference is) with dual outlets on each. I suppose a high-flow cat could be used too, but not sure what effect on performance/sound that would give.