im not sure if every hid kit(for 5th gens) makes you connect it to the battery but thats what i had to do for mine. my question is, since im already running power to the battery from my amp/sub, would it be a good idea to get a grounding system(ex. apexi grounding system) or a capacitor for my system or would everything run smoothly just the way it is?

 

The mass of the chassis is more than sufficient to supply a grounding path for everything in the car, but if you want to do anything - install a supplimentary woven strap cable from the chassis to the battery - terminal.
Wiring HID's shouldn't be much of a problem (except switching) since they traditionally draw no more than 35amps, as opposed to the 55 / 80amps of a conventional Halogen system.

P