Door speakers impedance
 

I have a new head unit, a budget 50x4 Kenwood that is rates at 4-8 ohms.
The right front speaker in my 2002 Xtreme is buzzing so I'll replace it. It seems to me the new speaker impedance should match the impedance of the other speakers which I believe are 8 ohm. However I would like to know if a 4 ohm speaker would do okay.

You should match the left and right speakers. Front vs back doesn't matter as much, but it would be best to match left and right as the amplifier for those will be built into the same circuitry. Likely you won't wreck anything with mismatched speakers left vs right, however it will very likely sound VERY weird with the lower impedance speaker sounding MUCH louder.

Thx. If I replace both door speakers will still be able the hear the front dash speaker? Or maybe I should put resistors in there to even things out? Or maybe the Kenwood head unit (4-8 ohm) adjusts for any difference?