aftermarket head unit with....

I've got two questions. My 4-way amp took a crap and sad to say I won't be buying a new one for a while. That being said I want to use my aftermarket head unit to power either
the factory speakers with factory wiring(components in frt, 2-ways in back) or aftermarket components in the frt, aftermarket 3-ways in the rear with factory wiring.

1. powering the factory speakers I assume is as easy as buying a wiring kit in order to wire the speaker leads from the radio to the harnesses. So I should assume somewhere within the factory wiring they have resistors built in so as to send the proper signals to the tweeter and mid in the frt doors? I thought I saw a resistor on the tweets??

2. powering aftermarket speakers I assume is as easy as buying a wiring kit in order to wire the speaker leads from the radio to the harnesses. So I should assume I can then tap off the main leads in each door to power my cross-over for the components in the frt doors?
Thanks in advance. I did some searching and just could not find the answers I was looking for

 

I've not seen an HU power component speakers very well. Typically the HU's power per channel isn't enough. Stock speakers it will rock the piss out of them.

As for wire, you connect the leads from the HU to the leads for the stock wire and you are good to go.

 

you are probably right. I think I tried that originally, forgot about that.