Sub Box to fit under 2009 Silverado CC seats

[doublej]

I'm looking for a premade box to go under the rear seats of my crew cab. I have found two manufacturers that look decent:

http://www.proboxrocks.com/products/loaded...000/index.shtml

or

http://www.subthump.com/crb07.htm

The Probox comes with it's own speaers in them, not sure if they are any good...

I have a 1500rms amp that I was planning on using.

The Subthump has about .83cft for each speaker, If I was to go with that setup what would be the best sub out there that would work in that small box. How would DC Lvl III's 10's work in that sealed box? I notice anything above that it's not recommended sealed.

I know the best solution would be to make my own box but I honestly don't have the time or know-how to do it.

Thanks for any input!!! Great site, been learning tons