Your GSX muffler, isn't going to be any different than the stock muffler you have on the car... they're the same car afterall.
You want a cat back, or turbo back (even better!) exhaust system, probably 3" stainless to begin with, if you truly plan to go as fast as you say.
You can buy them pre-fab, or have them made up. I've heard that Buschur's is pretty good, but loud. He's probably the closest place to you, since you're in Windsor. (He's in Norwalk, Ohio)
Failing that, Marco at Magnus in Toronto, is the next best bet.
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Andrew Bienhaus -
Web-Team Dude1997 Eagle Talon TSi AWD