You'll need about 1.25 cubic feet for a sealed box. I'd stick with sealed unless you want to lose all your space in the back haha. Also make sure it is pointed to the back of the truck or downfiring. I'm using a prebuilt box(I'll find the link) that's made for the rangers. Its slightly smaller than what your sub calls for but just slighlty(you could always use some polyfill or buy a spacer ring to mount it)
Also I lined the box with dynamat
I just picked up an infinity as well and from what I gather they can take a beating as far as how much power you can put to them!
I'm putting about 450 watts to mine which is rated at 350 watts. Sounds perfect to me!
Fabtech spindles,AAL and Belltech 6400's, 35/12.50/15 General Grabbers, Richmond 4.56, Ford Racing Trac-Lok with kevlar clutches, 31 spline expo 8.8 with discs and welded tubes, 15x10 drifters, fx4 interior, Mcqueen Prototype hood/front bumper/front fenders/bedsides