Is Polk Audio a good subwoofer to put in my 2004 Mustang?

righ now i have a fi q 18". my first sub was a polk audio db 12" sealed. comparing the two. the polk was in the same range in sq as the fi q" not the loudest sub, but they sound amazing! im currently using mine in my home theatre in a down firing setup tuned to 15 hz. they are probably one of the best deals in the industry for the way they sound. great and solid subs. I currently have 800 watts rms going to it in my ht.