I never liked the idea of using the head unit to power the speakers and/or subs.

Instead i ran a entire new and high quality wiring and left untouched the factory wiring.

I purchase four good ( and expensive,though ) RCA wires to hook up the head unit to the digital EQ,then connected the amps with the EQ.
The results : better,quality sound.

Both,speakers and subs are all powered by the two four-channels amps,one for the speakers and the other exclusively for the subs (@ 4 ohms )
Thanks to the digital EQ I can squeeze better sound from the head unit instead of relaying only on the built-in EQ.