Most people seem to go for the full system. Not sure what tailpipe options there are, but you can pretty much guarantee that if you get one from k-tec racing itll be loud!
If you dont want it really loud a Magnex will give you the rumble youre looking for with out annoying the neighbours too much. Dont think Magnex can offer a single 3.5" tailpipe though, just twin 3.5" or 6x4 oval.
If you decide to get a k-tec system join this club first and youll get a discount which will cover your membership fee many times over!