Grounding Question

[Yoshi]

if all your stock grounding straps are fine, chances are that regardless of ga, it won't make a damn bit of difference.

"hyper-grounds" and the like, are like changing your plug wires or fuel filter... you're not really gaining power, so much as replacing what you might have lost from age and wear/tear. Not to say that you won't get a small gain... it makes things generally more electrically efficient, and that's ALWAYS a good thing.

To answer your question 8ga is just fine.
Is your car having grounding issues already? Maybe you'll see a big improvement, but otherwise I'd look at it as a backup system for your old stock grounding straps... I've also heard people say that the hypergrounds help people with larger stereo setups who get line noise.