Question on wiring to aftermarket head unit

[jimmione]

Hello, I'm a new member here and am in the middle of installing a complete aftermarket system in my 2005 X5 that had oem Nav and no DSP. I gutted the entire OEM system. I've installed a JBL MS-8 amp/processor, a JL Audio sub amp and a sub. All that wiring is done! I've installed the double-din head unit bracket purchased on ebay (that's a story by itself). Now, I can't seem to find where to pull the power/ground and switched power from. I found a wiring schematic for the car. I could go to the fuse box. Can anyone who has done this tell me if I can simply cut and solder 3 wires from the nav head unit/ monitor harness and which ones they might be? I'm this close to having music in my X again!