On most decent amps you will have 2/3 input channels as u've said. I've used the Front head unit cables running to the amp, then i have splitters which split the RCA cable into 4, i.e Front and Rear. THis means when i turn the head unit on, i can set all the sound to the front and it'll come out of all 4 sets of speakers.

Try to get pictures and i'll try to explain it better.

wa wud b best 2 connect then? its unpluggd at the mo will prob only amp sub an 6x9s an run fronts off the crossover an hu

aye it depends what you are powering off them. If you are powering fronts then connect the RCA's to the front input. The loads of turney knobs are ur crossovers and gains :)

get pics but what are you amping??

if ya amping front speakers then run the rca leads into the front's same for rear speakers and a sub

ritey im almost ther, iv got the phone lead pluggd in2 1 of the rca points on me h/u, on my amp ther r 3 inputs choices 2 plug the leads in2, front, rear and sub which 1 do i use cos thers loads of turny knobs etc nxt 2 thm, if its easier i'll get a pic 2moz cheers