Shouldn't be too hard. I've got either a mach or audiophile enclosure with amp and sub on the way that I picked up off ebay for a little over $39 shipped. I think all I may need to mount it is an bracket, different carpet piece, and maybe drill a hole or two.
Plan on boring it out and putting a 10" in there and use my existing amp to push it. Definitly will beat having a heavy ass box sliding around back there!