reduced sq with lower impedance?

This paper however had ample information to back up it's claim.  I especially liked the comment about driver production tolerances having more effect on system Q than damping factor will. 

This is definatly an interesting topic and debate.

I deal occasionally with the Alpine PDX amplifiers..thier specs (power and distortion) do not change if running at 2ohms or 4ohms.

I recently had a situation where I was running 2-3ohm W7's to the 1000 x 1..which only has a 2ohm rating. Not surprisingly, the amp could not handle the load wired in parallel (blew the fuses on the amp casing) so we re wired in series giving a 6ohm load. I did not notice any difference in output or sound quality.

I have not done any tests using a 1ohm stable amp wired to a 4ohm load so has far as the OP, I can't give a conclusive answer.

I am wondering if the effect of damping factor has more to do with the specific amplifer, rather then simply using the final ohms load by itself to pre-determine if any noticable difference in sound quality could be predicted. As I read more info on this topic..I find it leaning more toward being an amplifer spec and not really coming to anything conclusive result about how it effects sound quality. Being that we are dealing with a vehicle environment, electronics and equipment, vs. home audio tested in a chamber, I question what the actual application of damping factor has do do with real world car audio systems.  Does anyone else see where I am going with this?