I have a '00 Bonneville SE. Since aftermarket cat back exhaust systems seem to be slim-to-none, any idea if a factory dual exhaust from the SLE or SSEi would work? I would think it would be a straight replacement -- would there be any benefit from doing this?

A good exhaust should be able to custom build ANYTHING! Better flow & therefore more HP would be the result.

Custom exhaust is the better way to go, but list or describe how far you want to go with the car so we can better help you with your exhaust options. And by the way, the SSE and SSEi'* are not dual exhaust, it'* single and the muffler splits it into 2. I was thinking of trying dual exhaust but in reality it wont make a difference and its just extra weight and cost. But I was also thinking of producing a cat-back exhaust for Bonneville'*/Grand Prix'* that are much less inexpensive than the other ones w/ stainless steel tips. Just thoughts.