First off, this site is a wealth of knowledge. Second, I figured I would put this here incase anyone else might be having the same issue.
I learned yesterday my drivers door speaker was not working, so after doing a bit of reading here and on a few other sites the google machine hit on, I grabbed my multi meter and set off probing 
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All speaker channels from the SC-816 output about 20mV DC. I am not sure why I thought it would be more but it is pretty low. The fact that all channels had the same out put from the HU and were with in a few mV at the speaker connector I was pretty sure the problem was not wiring or the HU.
So the next logical was step was to replace with a known good speaker. I took the passenger door speaker and plugged it in and low and behold I got clean clear music. That verified it was the speaker as the culprit, now to figure out why.
I could not find any clear information about the internal resistance of a voice coil. It should be close to what the impedence is with my limited electrical knowledge, so I started probing again. The good speaker had an internal resistance of about 4 ohms, oddly enough it is a 4 ohm impedence speaker. As I pushed on the cone it would changea bit, not much but it would move.
The bad speaker had 800 ohm of internal resistance, it would move too when I cycled the cone but it went from 800 to 1K ohm. I could not see any indications of overheating so I am not sure why it was so high, but it seems with resistance that high the 20mV doesn't have enough umph to push the driver.
Like I said this was all informational incase someone else is having similar problems.
Third and final, I don't have a CD Changer but for some reason I have a cable plugged into the CD port on the back of the HU. Like I said it is a SC-816 with no prologic or amp that I can find. Does anyone know what that cable is for?
Thanks
Ira