Need Metra 70-5521

1. This harness is actually 2 plugs- one for power, ground, speakers and the other for the subwoofer- so it'll do both.

2. The factory sub uses an external amp (seperate from the headunit).  I'm not sure where it is (although it's not in the engine compartment AFAIK), but it doesn't really matter- if you wire up the harness, you'll be good to go.

3. This is probably true, since subs usually do use the most power in any system.  No, the factory amp will not be bypassed, merely integrated.

Thanks.  I actually got through to Metra tech support today (on a Sunday)!

They confirmed that the 70-5521 will not bypass the factory amp that powers the factory sub (both are in the rear passenger side quarter panel).  So the 70-5521 will retain the use of the factory amp and factory sub while allowing for the addition of an aftermarket HU and aftermarket amp (for the door speakers).