I am helping a buddy install 2 12" P1's in his 2008 G6. He has to remain using his stock HU, so what would you guys suggest to be the best way to wire subs up? Note: his HU doesn't have any RCA-outs. It's all speaker level. I thought of tapping into his rear speakers and using a LOC, but didn't know if that'd work. Thanks in advance guys!