The "drill into it" suggestion was not too far off the mark. Have a look at my post at
http://www.ppbb.com/boards/ppbbphp/showflat.php?Cat=&Board=ARCHIVES&Number=1085350&page=&view=&sb=&o=&fpart=all&vc=1
and
http://www.986forum.com/forums/showthread.php?t=5059
These posts should give you something to think about. I wasn't prepared to spend big $$ on a minor improvement in sound that resulted in no HP increase. Some of the aftermarkets systems are just way too loud. I was also not prepared to bypass the cat, as the boxster is a convirtable and i would have to cop all the ill fumes at traffic lights.
I have drilled my exhaust to bypass internal chambers somewhat. Externally you cant pick any modification to the exhaust. Its louder but not by much. If i want it louder i can just increase the size of the holes.
Im suprised more people have not done this.