My 2 cents, others may disagree:
From my experience it is more of question as to how well you tolerate drone which typically occurs between 2500 and 2900 rpms. I purchased my Boxster S used and it came with the B&B TriFlow system already on it. Much throatier sound than stock and I loved the burble during deceleration, but, after a year or so it really started to annoy me, that's me.
From what I have read over the past several years if you want great sound without drone you have 4 options:
-The Porsche OEM PSE (Porsche Sports Exhaust) exhaust option, pricey.
-Crios Exhaust Mod, it is simply modifying your stock exhaust with drilling.
http://986forum.com/forums/diy-project-guides/19770-diy-exhaust-mod-%96-gain-10-hp.html
-Pedro's Exhaust Mod, search for it here.
-Fister Exhaust, not widely known in the Boxster community but very well known with 911 guys.
http://fdmotorsports.net/fister-exhaust-boxster Great company and great people to deal with.
Here is the same set-up I have on my old 911, great sound without a hint of drone:
If you don't care about drone (it usually takes awhile to get on your nerves) buy Chinese / Cheap. An interesting article:
Pelican Technical Article: Installing a Performance Boxster Exhaust System - 986 / 987