[Stl-986]

Here is my take on it.

original speakers I believe are 8 ohm (threw all my old ones away so I can't verify). Installing new speakers and using the oem amp is going to cause issues. New speakers are going to be 4 ohm. Quality wouldn't be much a issue, but power will be connecting things up.

The better setup would be to just run rca cables to an aftermarket amp and ditch the factory amp. You could connect the low level wires from the HU to the factory amp to the new amp, but rca cables would be better. It really isn't that difficult and is pretty quick to do. You also dont need to run a turn on wire as there is already one at the HU & amp, just use it.

I am also not a fan of using the Metra or others wiring harness. Not that expensive, but it's just easier & quicker to just cut off the factory connector and wiring things. if you use an afttermarket amp you only need 12+, switched 12+, ground, antenna power, illumination and turn on wire. The rest can be capped off.

What you need to do though is to look at the entire system, your goal, budget, etc and plan accordingly. For example, if you get a HU that only has front/rear rca pairs & a single sub output you need to plan your amp accordioning as well as your wiring. Some amps will have a pass through for connecting a sub amp, some wont. if you only have a single sub output you should connect it to an amp with a splitter so you get the amp to output both left/right for the door speakers. If you want to eventually add the rear speaker tray & speakers, take this into consideration. Wiring isn't that difficult either. You will pay more for HU that has all 6 channels out but it isn't that much more.

There are just so many more options available if you ditch the factory setup when replacing the HU.

When you do want to do the rear speakers let me know I have a kit that is way cheaper then factory.