I'm thinking about upgrading the speakers in my truck. Is there a pre-amp line out on the factory head unit? I have the Sync setup and will not be replacing the head unit.

 

I never messed with a pre-amp output, never searched for it. What I did was replace all the factory speakers (tweeters and mid-ranges in the doors and pillars) using the fitment guide based on the '08-'10 model years at Crutchfield.com.

Then, I installed a line level converter to the left and right rear channels at the speakers in the rear which gives you a left and right RCA type plug for output to an amp to drive a subwoofer. This is available at O'reilly/Autozone/Advance auto part stores in their audio section.

You could install line level converters on the front channels too and use the signal to drive an amplifier for all your speakers, however you want to handle it.