speaker wire, 2000 ford f150

I'm wiring my new door speakers tomorrow, the F150 is a 4 door ext cab, and the only problem I see is running wires to the rear speakers. Is there a way to fish the wire through the door and into the truck without having to pull the rear seat and the molding in the cab. Theres only the speaker wires that run into the rear doors, nothing else electrical. The rubber boots for the wires between the doors and cab, are just that, no wire harness to go through. The front doors, are easy to access. Any help would be greatly appreciated.

run everything from the amps to behind the head unit and just splice the wire there.

-------------

Running the wires from the amp behind the headunit is a good easy fix to your problem but be sure that your factory system is not amplified.

-------------
Where theres is a wire there's a way.

Ok, I've wired the front comp. speakers directly to the amp. Now I'm looking to splice into the the rears. I've got a Metra wire harness, for ford 1998-up. But I don't have the bag it came in,(had the wiring color code on it) does anyone know what the wiring color codes for that harness are?

The HU is a Pioneer DEH-P4800MP, forgot to add that, if it helps.

Ok, I got it all figured out, I'm new to all this. It took 8 hours to dynamat 4 doors, run speaker wire through the front doors, (drivers side is very difficult), mount my alpine amp, run all the wires. I'll try to dial the amp in tomorrow. I don't know how you guys do this for a living, it's hard work. The way I look at it now, what you pay for a good install is worth every penny. And I'll be on the paying end of it next time.