Will an aftermarket stereo system support all 6 of the factory standard speakers installed in my vehicle?

Question

2003 Hyundai Sonata

Answer 1

You may want to check them out and see what their impedance is.  Many factory systems use a much higher impedance then after market stuff.  It cuts down on the demands on the electrical system.  

As long as the speakers when measured at the head unit wires measure somewhere between 4 and 8 ohms, you should be fine.  Otherwise, you may want to shop for some speakers too.

Answer 2

Yes because you only have 4 full range speakers and to tweeters the tweeters are hooked up thru a high pass filter so you will be okay