My buddy has a 4Runner and I'm installing a new 4 channel in it. It has a factory 10 channel I believe. It has stock JBL system so the rca's only the F and R ones coming out of the deck go into this digital interface that maintain his stock sub and center channel. The other side of the interface is a mess of wires that go to his stock amp I believe. Can I just spilt the RCA's before this interface and send them to the new amp as well?