Most spec boxsters in my area run straight pipes. I couldn't stand the noise (even with earplugs) so put together a home made system that resembles this one:
Exhaust Muffler Silencer Set with Cat Bypass - 986 BSR - Boxster Spec Racing By Patrick Motorsports Porsche & Mid Engine Performance Specialists
Mine uses a couple of magnaflow 4" round straight thru mufflers 14" long. The pipes with the flanges are from a factory exhaust and the output tubes I had bent up at a muffler shop.