bose stereo upgrade

I own a 2004 pathfinder. I want to upgrade my sound system to bypass the stock amp and add my own powering the existing speakers and adding a sub. Are the pre-outs from the headunit compatible with an aftermarket amp? (i.e. do they have a zero or floating reference) I have also heard that the impedance of the stock speakers are 1 ohm. I read on an older thread that there is a device that can correct this. (PD3/PD4 Audio Link) Has anyone successfully performed this mod? If so, what components/setup did you use?

Thanks, tklein78