I have a US Acoustics 800D mono class D amp. It is this one : http://www.crutchfield.com/S-mTuMf75...235USX800D&s=0

It is 400 watts x1RMS at 4 ohms and 600 x1 RMS at 2 ohms.

I also currently have a 15" Pioneer that is 350 watts RMS and i have it hooked up at 4 ohms so it gets 400 RMS. THis is the sub :

Oh yeah, and I have a 1/2 farad cap.

Alright, now that you have all the info about what i got, i have a question for you.

I was wondering what is the best single 15" i could hook up to this amp. This pioneer sounds pretty good, but i know I could get louder. The best thing I could think of doing is getting a dual voice coil sub so i could get 600 watts out of the amp at 2 ohms instead of the 400 watts I have now with my sub. I know a lot of you will say to get 2 12s or something like that, but I just want one 15 cause i already got the box and everyything. I like a sub that can be loud with rap but also good SQ for stuff like rock music and stuff. The pioneer does this, but i know i can go louder. Anyways, what do you think. Dont just give me your favorite 15, but tell me something that has a power handling that will nicely match my amp. I would really appriciate it if you all helped me out. Sorry for the long message, I am just trying to give as much info as possible.