Meat,
I too hate the lack of bass in the box... there are a LOT of ways you can go, BUT if you are not willing to invest in a better head unit (OEM sucks imho) then ask yourself what quality bass you will get for the money you are willing to pay...
Also that enclosed sub requires no other amp (pro) but now you have mounted a sub right next to your ear (major con). Subs as we know are meant to be felt, not heard, imagine the extreme discomfort of "feeling" the sub right next to your ear, MAJOR HEADACHE!!! also I noticed that particular sub didnt have a remote. meaning once wired in, you will have to use your head unit (stereo) to control the bass out put... and that is even more frustrating. Last reason to avoid that enclosure, for the price, you could custom build one in that same space thus getting MUCH better acoustics!
So whats a man to do to get some bump and not break the bank?
upgrade the door speakers or dash speakers. Read this
http://images.wikia.com/boxster/images/b/b6/Boxster_speakers_update_article.pdf
Dont want to do that? good cause i wouldnt! im going this route (seat shaker)
Aura AST-2B-4 Pro Bass Shaker 299-028
It is shocking how well these work especially in our tiny lil Boxsters!!!!
just some food for thought.... yummy