Pioneer has some 10 and 12 inch flat subs. They sound pretty good, but I hear that theres a few other companies making them now. I haven't listened to any of those, but the Pioneers hit pretty good. In a hatch car like the Z, they're going to be PLENTY.
I heard them in a convertible. So I can only imagine they're going to hit way hard in a hatch. I think the 10 inch was a 1K watt and the 12 inch was 1500 watt.
Found a link:
10"
Pioneer USA - Shallow Series
12"
http://www.pioneerelectronics.com/PU...201S2|S4?tab=B
I personally like JL more, but if you're looking for space, these are pretty nice.