what if I tap into the power wire of the headunit wiring harness to power my amp instead of straight from the battery, I know it will probly work but im sure there are downsides becasue my friend did this with his altima.

 

I would think that would defeat the purpose of having the amp - it would be able to draw much less power than if you wired it to the battery. Just do it the right way...

 

try a little experiment: listen to what it sounds like in your friends altima with the setup he has now and then power up the amp straight from the battery. See what you like better. If there's no difference, oh well...

 

Wire the amplifier directly to the battery with a remote turn-on lead from the head unit. Don't forget an inline fuse as close to the battery as possible.

Tony