Ditch that sub, amp and cap. Money can be better spent else where, and I don't even know which models you have selected but punch series is crap imo. Rockford is a great brand, I have a T1000-1bd and 2 T115d4's, but I'd never consider rocking something they sell through best buy.
I worked at Best Buy for four years and we carried punch, power and T-series subs. Maybe just not from the town you were in. It was generally only in large stores, the same stores that had the magnolia stores inside. I had a T1 15 that would give nose bleeds from scrambling your medulla ob-lon-ga-ta! However I sold them all when I quit in March, which makes me upset, seeing as I had a p3 12" I sold as well. I would have liked to put that in my fit. Now I must start from scratch.
I think your build looks like it will be great. Working carfi for 4 years, I have seen kenwood's hit harder than expensive stuff just because they handled power better. Getting your system squared away with good parts from wiring to amp is the best way to go. A lot of people blow the biggest amount on the subs and skimp on the amp and it sounds like crap.
