If you want some nice subs, check out
www.audiomobileinc.com The MASS is what you are loooking at. Them, Orion HCCA's, DDAudio subs, and strokers are some of the loudest subs you can buy. Also Crystal CMP is a nice sub.
Stroker's are SPL beats, period. They CAN be capable of SQ if you make them.. but by nature they are power loving high SPL in your face no holds barred LOUD subs, period. HCCA's and DDAudio subs are very close in SQ and SPL, and the MASS are a BIT more SQ and a BIT less SPL. Honestly, if you are making a dailt driver and not an SPL machien for competition, I would stear clear of the Strokers and go for the MASS.
NOTE: All of those subs NEED good power.