i wondered where the v from svs ended up...guess it was to start powersound.
given that he is the guy who designed that one, it is probably a pretty good performer.
that said, there is only so much to a subwoofer.
in the case of the xv30, two 15" drivers, a 6" precision port, 750 watt plate amp, and mdf enclosure, and some sort of duratex like coating.
my guess is that it is tuned right around 20hz.
two 15" drivers only need to move about 10mm in order to hit the 117db@1m spec on the website for 20-31hz, so the drivers don't have to be anything remarkable.
so if you can build that for less than $1400, i suppose it is a good deal.
as for making it look pretty, that is up to you. there are a million options. have a look at the diy gallery.