personally i would run 2 runs of klmx over the copper wire its only $0.10 per foot more and you will have more power flow with 2 runs of cca over 1 run of copper
so let me get this straight you are as bold as to say that any aftermarket header/exhaust manifold is going to make a car sound like a "riced out retarded piece of fail" and that a factory one is going to sound better ha. you my friend are a funny guy.
i just wouln't trust one battery to keep up if you are beating on it i don't think that it will keep up put im no expert just a hobby kinda guy but i say better to be safe than sorry