You could go for one of these:
http://www.cardomain.com/item/KICPACK02
Not too expensive. By the way, as for 400watts not being that much power. I currently have my 15" L7 running on 50wrms in my room, and it's extremely loud on max volume. You can still get lots of bass without lots of wattage.

 

thanx 4 takin the time to answer my retardo questions man lol i appreciate it how about this one ??
http://www.crutchfield.com/S-k28SqAu...20&I=489AP1000

 

Yep, that one would work pretty well. Those infinity subs are pretty sensitive, so you don't need as much power to get the volume with them.

 

the good thing about those subs is they don't need allot of power handling