when you have a high powered system like....4800 watts total....and you buy a 5 farad cap, which is recommended for 5000 watts systems, would you still have to buy a battery just to power your system or should the cap do all the work just fine?
with that much power, that cap isn't going to do anything. even though you get an extra battery, you still need something that will charge those batteries. your stock alt isn't going to cut it. i would first upgrade the alternator and then get the battery and cap.