to split the power cable you will need a power dist. block. ok before i go any further why do you need all this stuff split? if i may ask. are you trying to run 2 amps? let me know and i will try to help more.
You will need a distribution block like Hunter said. Although you'll probably want to run 0/1 cable from your battery to your dist. block, then run 2 or 4 gauge in short distances from your dist block to the amps. You will have to run extra wiring and another set of RCA cables, regardless.