Connect all 5 channels from headunit to 5 channel DSP/amp

Hey folks,

Recently installed a 5 channel DSP amp (JL VX1000/5i). The wiring kit I used had a very long 6 channel RCA cable.

The head unit and amp are very close and I'm wondering if connecting up all 4 channels is really necessary? Can I just control everything via the DSP and use a high quality L+R RCA instead?

Cheers!