There are a bunch of YouTube videos as well, some of which do a nice job with showing the stock vs the new one, and not having tons of other stuff changed.
+1 for checking out a meet and hearing some options.
Personally, while the Z is a huge upgrade for me and sounds good to me stock, I will someday also upgrade mine, but probably with a Tanabe (Japanese car...Japanese parts...at least that sounds good). I like their sound, and don't really want something loud-look-at-me, but rather something that makes me smile; and bass clarity makes me smile.
Something to deepen out the running sound and give it a better start-up than stock. That's really all I'd want.
Always hear good things about the FI exhausts though, and they sound excellent.