Help with amps & pots & 8ohm & 4ohm speakers

[Bones]

I should firstly apologize for not searching, well I did, but I didn't put the big effort in when I am sure much of this stuff has been answered.

But here goes.

I will run a dual log 100K pot from soundcard output to amplifier/s input.

I have butchered some PC speakers. Inside where 2X 4ohm magnetically shielded speakers and the amp that powered them. These are of no major concern.

However I also what to run another 2 car speakers which are also 4ohm and I also have some 8ohm magnetically shielded speakers from a TV set.

Despite the number of speakers, all I am interested in is R & L stereo, I am not looking for any type of surround..

I figure I can share the one volume control to adjust volume on all the speakers if each amp gets it's own signal (after going through the pots). One question I have is if I double these pot outputs, does as much power get fed to each amp or does the input signal get halved?

The one thing that would make life very simple is being able to use just one amplifier that will work properly with 4ohm & 8ohm speakers. I know a car stereo will run 4ohm speakers, what happens if I was to hook the 8ohm into this as well? Do I fry them? Do I fry my stereo? Will my cabinet catch on fire causing my children to cry?

Really, at the end of the day I am trying to avoid having a second amp, do I have any options that may work? I have underestimated the audio knowledge required in my project and any help/suggestions appreciated.

** Ohh yeah. My plan was to have a switch so the car speakers could be switched off, I mostly wanted them installed for music rather that Galaga. Thought it might be worth mentioning.....

[Crazy Cooter]

The one thing that would make life very simple is being able to use just one amplifier that will work properly with 4ohm & 8ohm speakers. I know a car stereo will run 4ohm speakers, what happens if I was to hook the 8ohm into this as well? Do I fry them? Do I fry my stereo? Will my cabinet catch on fire causing my children to cry?

http://www.bcae1.com/spkrmlti.htm

[Bones]

Thanks Cooter. That link helped a huge amount and I have worked out how to get around my problem.

No wonder my searches were coming up empty, I had the terminology wrong. Impedance was the magic word I needed.

[richms]

Impedance is only half the story, there is also efficiancy, if you have a really efficiant 4 ohm speaker and a poor efficiancy 8 ohm  on the same amp, th 4 ohm will take more power, and will be a lot louder meaning the 8 ohm may be so quiet you may as well not have it there. If you series them up, the 8 ohm will take more power then the 4 ohm and the volumes may be better matched.