Often I wonder if there is a difference between someone who is a sociopath and someone who is a narcissist. I did a piece once on the difference between bullying and a control freak, because there seemed to be an overlap in that area as well. Sometimes it is best to go to the actual definitions to eek out the differences between some of our similar yet different meanings.
Here is some interesting sources of information on the qualities of a sociopath:
Profile of a Sociopath
How to Spot Mr. or Mrs Cold or Charming
Here are some interesting sources of information on the qualities of a narcissist:
The Sheep and The Wolf
Discussion on the Difference Between a Narcissist and Sociopath
Narcissist or Sociopath, What is the Difference?
Basically, it seems that in order to exist, the Narcissist needs YOU (or their victim) to validate their special rarified existence.
To a Sociopath, YOU (or their victim) are but a plaything, and a means to an end.