I think an X-pipe w/ a flowthrough muffler is about the closest you're gonna get without swapping to one of those engines. Its not completely the exhaust system that gives those cars the sexy exhaust note.
If you wanna go extreme(without spending a ton for an exotic motor) to get that sound, your best bet will be a lexus V8.
http://www.youtube.com/watch?v=QtgoFrDGBFE&feature=related
but who wants to go through that much hassle for an engine that doesnt have a ton of aftermarket? and will have half the people on this site calling you unamarican(misspelled for annunciation purposes