Well go with 2 15in sub in a seald box

Those are some bad sub Iv never heardthem but I have heard the SQ is real good
For the money Y? dont you go with Audioque 15's there a little less expensive
and they have the flat wound voice coil option too for a little more $$ and as far
as SQ goes there great if not better than the gti's But they dont believe in sealed
boxes though, So two 15's in a ported box will be huge
http://www.audioque.com/aq/HDCSeries.htm
Or DDaudio Is awesome like the 3500 series
http://www.ddaudio.com/