I don't see the point in spending big bucks on full exhausts or even cat-backs unless the tubing is bigger and your engine needs the extra flow. Otherwise, the exhaust doesn't give a shit about what brand or quality of metal pipe it's going through. If it's in good shape, the stock exhaust pipe is fine. Just swap in a free-flow muffler and call it done.
As for the shorties, I don't think they're worth it even if you didn't get them for performance. Headers let so much more heat into the engine bay, which dryrots and ages the wire loom and wiring, hoses, etc. Headers in general are also known for having less-than-optimal couplings that are notorious for leaking. That 10 HP you may gain from them isn't worth the headaches they can bring. IMO, it's either long tubes or nothing. Even then, I'd highly recommend coating and/or wrapping them.