There's LOTS of good stuff out there, especially for the size of your Navi
I'm pretty sure NY is tight on emissions, Cats, O2 sensors and OEM emission controls.. messing with the exhaust system any more than adding tips might get you in trouble down the road. Better check with some locals on that one.
(for your other thread)
You'll need DVD screens, Navigation GPS, Huge Sub woofers, Amplifiers, speakers, etc.. in short.. $$$
Try this link
for some ideas on what the other guys are doing. Expand and view the Audio/Video section.