Looks like a GHL to me too. If that is the case, they sell for $1K new and you could easily get 600 or 700 for it used. Just buy some metal polish and shine it up nice and put it in the classified section for sale.
Drove around today with 2 sound meters. Top up, windows up. The more professional one hit 96db. The cheaper one hit 110db. Both at 2500RPM. Definatley not safe levels for daily driving.
If I were wnting to replace the aftermarket exhaust you have I would definately go with the 02 Boxster S if the gentleman here will cut you a fair deal this is what I have on my 2002 Boxster S and I absolutely love the sound...by no means annoying but still deep and throaty I couldnt ask for a better sounding non annoying system....plus you could probably make money selling your aftermarket setup