Usually longer port=lower tune freq.
You should down load the torres calculator and play with the port length. Or the psp port calculator should work also.
With your subs coil configuration most likely your going to wire your subs at 2 ohms right. I would look for a amp that rated at 1500 wrms at 2 ohms. IMO Maybe look into a audioque 2200.
IMO I would get the alternator first. Which alternator are you getting. If your funds are kinda low you might want to check out sears yes sears the sell diehard platinum agm battery's. If you get a diehard platinum make sure it's a marine batt (the blue one)group 31 or 34