I was previously running an elemental design 15" sub. It was fantastic. Ran a jbl 1200.1 which i'm still running except on an FI Q 18". I drive a '95 beamer and was able to fit a ported box in the trunk with the 15" just by dropping it in. Sounded fantastic. I had to build the box for the 18" in the trunk. sub first, then faceplate, then rest of box pre-assembled. It was such a pain in the ***, but worth it. It's sealed, but soon i'll be building a ported box for it. WEEEELLL worth it, both the 15 and 18 sound sooo much better and deeper than any of my previous 12s.

 

I have a 15" in my Alero trunk ... it barely fits (in height) but I've managed ...
It's just nice sometimes when I open it up and most people go "Holly ****" ...

I'm impressing the unknowledgeable though lol

My next subs will probably be 12's just because I like the size.

 

right now i running one 18 for daily ground and pound in a 240 sx and a small box and love it

 

got two 15's in my ford explorer, had the same two 15's in my honda accord. Box is sealed and i love it. IF you have the room 15's are the way to go.