Seriously? I think you need to do some reading on how these things work. Big 3 is an internet trend that's gotten out of hand. Maybe I'm wrong but I'm doubting your stereo equipment pulls enough power to necessitate a new alternator + the cables necessary to transfer that extra power. I will admit though, 10' at 8 guage won't allow a lot of amperage through.
I don't know the size on 04+ but it looked to be 8awg running to my battery too. I'm currently running 4awg to my trunk for 2 amps that can push out a max of 500watts(a/b) and 600watts(a/b). So I'm not the most efficient and even when I crank I don't think I've ever seen it dip below 13.4V on a real hot day. Yesterday driving home in 35 degree weather it didn't dip below 14.4V
Just did the big three... New battery... lights still dim. - DIY Mobile Audio
Now start calculating your needs.
WIRE
And to help others on spending...here's one on audio cables too.
the science of cables - DIY Mobile Audio