My friend got one of those universal (and crappy) canister exhausts off ebay and installed it on his P5. He took me for a drive and I braced myself for a high pitched whine, but it was a surprising nice low rumble (with the silencer in). In fact, it wasn't very noticeable with a conversation going. With music I couldn't even hear it. Without the silencer, it gets louder, but not to the point where my ear drums burst. And it's still relatively low. This is all good, when compared to my other friend's Civic with a universal canister exhaust. Man, that thing makes high pitched farting sounds, it bugs the hell outta me.
I wish there was something like the Greddy Evo exhaust for our cars. I saw a WRX with one of those, damn it's nice.