As far as the alternator goes you should give the fitzall 220amp a look. We couldnt find a high output alt for my buddies dakota and then we found the fitzall and it handles his Kicker zx2500.1 and 2 15" Kicker CVX's like a dream. He also has a an extra battery for it but the alt upgrade was def noticable. As far as subs go, i like your DC idea best. Also, go 12's.