There is a link somewhere of a youtube clip of a regazzon exhaust. personally I don't like the sound. It seemed too loud and rashberry ish, not enough of a rumble. The supersprint in the video sounded better. I think these were on the v6 though.
The prodrive for the 2.2 has the resonance chamber as was designed to give a classy sound, so although I haven't heard one, that would probably be more to my tastes.
I will shortly be needing a new midsection for mine and I am thinking of maybe a stainless system, but undecided at the moment.