Well, I would take that sounding exhaust over stock anytime. But Im sure itd get old on the highway so poof, its normal again. I thought about doing that too, where you just bridge pipe to the tip, but then you dont get the option of going back to quiet mode, and you wont be able to make it louder unless you get it entirely redone. And valvetronic exhausts are sweet, ive seem them for $10,000 for an M3.
http://www.vividracing.com/catalog/product_info.php/products_id/8147 That ones only 7 grand, what a bargain. They sound the best out of anything ive ever heard though.
http://www.kreissieg-usa.com/video.php?video=m3_3.mpg&desc=Video%203
Heres there boxster exhaust.
http://www.kreissieg-usa.com/index.php?page=detail&brid=3&mid=48&cid=78&oid=&pid=102
And a video.
http://www.kreissieg-usa.com/video.php?video=bx060113tuka02.mpg&desc=F-1%20Mode%20Highway%20Pass%20By