your stock electrical should be ok. you probably wont need to add another battery, but i'd upgrade the main battery you have. it'll help, and being an addict, you'll eventually get to that point anyways where you'll need to upgrade so better not to strain on it now.
the amp is a pretty decent amp. my friend had a kenwood amp a lil ways back, and not sure if it was the placement of it, but i think it was prone to some overheating. still performed nicely tho
4 gauge wire will be fine for the power you're using.
and welcome to the site