So i have a 2001 F150 that I have a Sundown Z v.2 12 in. The box is 1.8cubic ft at 32hz and It is being pushed by a Sundown SAX-1200d amp. I still have stock alternator and Red duralast battery. Voltage reads 14.4 and up at idle, but does go down a little bit when I play the sub hard. I dont really have problems pushing the sub right now, but I know I need better electrical. I plan on adding electric fans in the future so I need some electrical upgrades before I can. I have Big 3 done in 1/0 welding wire and all the wire to the amp is 1/0 welding wire. Should I just get One big battery and leave stock alt, or add 2 batteries with stock alt, or upgrade alt with One big battery. Give me suggestions on which battery I should get that will fit under the hood of a 2001 F150. Right now im guessing system is 1200-1500rms, but I want to have enough electrical so that I can run 1500-1800 rms and electric fans. What would you all recommend??