I have to agree on the insane sane of an upgraded Integra.
Best sounding car? That's rough. The Lotus Motor Sport Elise has a pretty cool, sound, I think, and the GT40. But I even like the sound of the NSXs.
As for the GT40, I think I remember reading somewhere that it was the sound they used in the movie, Bullitt, since they decided it was the best sounding engine ever. This was in '68, of course, and McQueen is driving a Mustang, but I think it's interesting. That and McQueen actually did the driving for the movie (and it's some serious driving, if you haven't seen it). OK, I'm getting way off subject, so I'll stop.