Best subwoofer for use in 1st gen Scion xB?

Ive owned a single 15" alpine type R and as for SQ type R's will defntly beat ur DD but as far as SPL goes dude for $400 ur not guna beat a DD lol (no offense) but DDs are aome aerious high power subs but in alpines defense its not a fair comparison to match them up bcuz they are in two different categories. But my suggestion is for $400 u can get either two 10" or prbly better in ur case two 12" type R's and they will defntly deliver the sound quality u are lokking for as well as some pretty damn good SPL (my 15 literally lifted my wipers off my windshield) on about 850 teue watts Rms.