Went in to a local dealer today to find a rear storage box for the 300 today since I'm heading out on a ride this weekend and wanted a cooler to carry some drinks in since it's been around 105 all this week. Didn't have the one I wanted to so the guy cut me a deal on this. Ended up paying $292 for the whole setup, lists on QuadBoss's site for $456.98 total. 3 coolers inside, 2 can strap on there in place of the speakers.
I'm pretty happy with it.