Under seat subwoofer

Hi! First Id like to thank everyone here for the help Ive received from this site. I just finished replacing all the factory speakers and I did it myself thanks to priuschat.

I have a JL 8WO-4 sub its only 8" a little small for me but I was wondering if anyone has made(or bought) a box for a small sub to go under the seat? If so what are the dimensions W*H*D. I would've went with the Kenwood mini but this JL was given to me a couple years ago and I'd like to use it if possible. The recommended volume is .375ft for this sub I'd like to get close. I was wondering if 12*6*12 would work(i haven't done a exact measurement below seat yet) that would give me .5 cubic feet (I think) that could be wrong on a different box calculator I needed a 12*7.3*12 to get just .375 cubic feet, and the mounting depth is 4in for the sub. I'm planning on running a JL E1200 amp to it (120rms 4ohl) it should work good for it (I think). I'm not planning on pushing it too hard. Thanks, your help is greatly appreciated.

Also to improve my sound quality I purchased a Belkin adapter I read it sounds better than the regular cable but when I hook everything up I get a terrible static, scratchy sound. Anyone know why. I have a ipod mini. Thanks again.