I picked up a Magnaflow (Car-sound) Catalytic converter and a Dynomax glass pack muffler for my 4 cylinder. And lemme just say... <img src="/forums/images/graemlins/kewl.gif" alt="" /> Damn nice sound.
Not tinny/ricey, low rpms have a very crisp low tone. Great lobeing.
$50 for the cat and $18 for the muffler. Can't go wrong. I'll post a video up of it or send you a link if you'd like to hear it.

2000 Audi TT 1.8Turbo Quattro
1988 Chevy Camaro - 100% Built + for sale!