I don't see how acknowledging that economics is about choice excludes   
Marx at all, or limits methods of analysis, or social phenomena.    
Sorry to be empirical, but I would like to hear examples.  
  
Clearly, for instance, one element of choice is the institutional   
framework (whether cultural or legal) that a society chooses to   
impose upon itself (or has imposed upon it); that frames choice.  You   
ignore it (as most economists in fact do) at your peril.  
  
Marx's cash nexus and his respect for the instinct of workmanship are   
also I think easily brought within the framework of understanding   
"choices."  And if you are Weberian, you recognize that in traditional   
societies there is very little choice at the individual level.  
  
This is a much richer way, I think, of understanding the insights   
that economics offers than the very narrow focus on satisfying   
material wants, which is where most introductory texts begin   
(unfortunately).  
  
Fred Carstensen