Those mufflers sell under a few different names for $279-$350 on eBay.
Yes, they are louder than stock. MUCH LOUDER. If you can live with the loudness, they sound awesome. There are also some concerns about exhaust drone at freeway speeds. Do a search on catback exhaust and you'll find lots of posts and info.
Which Boxster should it go on? My 2001 6spd S or 2002 Tiptronic Base? I am leaning toward the 2002 because of the improved look of the dual exhaust tips.
I have that exhaust on my 99 and love it. its lighter than stock and louder! I have found a Kick at higher RPM's. I also replaced my rear bumper with an 03 unit and so you can see the stainless from the rear diffuser. there is some drone but keep it above 3k RPM and its sweet.