hey guys

my car was previously wired for two amps, but when i bought it the secondary amp powering the components was removed. therefore i have the headunit powering the aftermarket components, which sound meh...

i recently picked up an amp to add to the rest of the system, but i'm a bit lost as to how i should hook everything up. i've done installs before, but since i didnt wire this one up i'm not sure how everything works.

when i slide the passenger seat up, i see a power cable, two sets of speaker wire (which i assume are spliced into the components already), and i see a set of RCA's.

what i need help with is:

1) if i have a remote 12v amp wire already hooked to the sub, how do i get another for the 2nd amp?

2) right now the headunit is powering the components, how do i bypass using the headunits power and use the amp?

3) what kind of fuse do i install inline from the battery? something thats rated lower or higher than whats in the secondary amp?

4) is it ok to ground it to the passenger seat bolt?

i think thats it for now... feel free to add anything i might have missed

thanks for any help