While a sociopath doesn’t think about other people unless they can benefit her in some way, a narcissist only thinks of others in terms of how they reflect back on her.
When you put these two qualities together, a picture emerges of a person on a quest for power and control, who uses the love and admiration of others as a tool to dominate and manipulate, and who goes about all of this thinking that it is his right and that he is justified. There will be no guilt, no apologies, and no remorse coming from the narcissistic sociopath.
Even if these behaviors land this person in trouble, or worse, in prison—he won’t stop. After all, it’s all just a game and the people are pawns. When he gets tired of those people or they aren’t serving a useful role in his life (his game) anymore, then he will cast them aside.
A narcissist without APD might have some ability to feel guilt or remorse and may be able to be helped with appropriate psychotherapy. A narcissistic sociopath, however, is unlikely to feel those emotions or be helped in a genuine way through psychotherapy. Therapy is a game to be manipulated and the therapist is a pawn.