if its for your taco & space is limited...i went with the mtx thunder thin 12's & they sound REALLY fk'n good! my buddy made a glass enclosure/amp rack behind the seats of my standard cab toy & you's be amazed. with the flat face on them, i think they look pretty good too (not the best looking ones i've ever seen, but still pretty cool)
http://www.mtxaudio.com/caraudio/products/subwoofers/IndexTThin.cfm
use those with the x thunder 1000xd & you won't be unhappy
http://www.mtxaudio.com/caraudio/products/amplifiers/xthunder1000XD.cfm