Well the frequency responce isn't that great on that Rockford fosgate box, it only goes down to 31Hz vs the 23Hz bottom end for the Infinity and less sensitivity, though having 2 subs may make up for most of that, though you could go with a pair of the single voice coil Inifinity's wired in parallel, it's a bit more than that Rockford fosgate, but not by a ton, $99.99 per speaker and $89.99 for the box.
http://www.crutchfield.com/p_1081260W/Infinity-1260w.html?showAll=N&tp=111http://www.crutchfield.com/p_236BS212S/MTX-Bass-Slammer-BS212S.html?tp=554And also probably want to get some polyester stuffing for the box if you do that since the optimal size for those speakers are 1.25 cubic ft and the box is 1 cubic ft, the stuff makes the sub act like it's in a larger box though.
http://www.crutchfield.com/p_027808/Polyester-Fiber-Stuffing-1-pound-pack.html?tp=655On the rear if you can swing the extra cost i'd go with the matching
polk audio 6x9's for the fronts, or a 2nd pair of those same 6 1/2's from the front with an
adaptor plate to match the speaker sound characteristics so it sounds better or drop down the fronts to the matching
Alpine 6 1/2's to those 6x9's. The only potential thing to check is what the min top mount depth is for you're car as the polk audio's are only 2", the alpine's are 2 7/16".
Or another option is a matched set of
infinity 6 1/2's up front and
infinity 6x9's in the rear, and the infinity's def won't have an issure for mounting depth in the front as they have a 1 7/8" top mount depth, though $20 more than the polk fronts and alpine rears combo, but it would sound better and you will get more bang for your buck with their higher sensitivity's.