WordPress CRM Plugin Recommendations, Please
 

Does anyone know of a Customer Relations Management plugin for WordPress that can do the following easily and elegantly? (Though any suggestion is appreciated!)

I need to have a customer-login for a site that will let clients see the work that was done exclusively for them and download it. Ideally they would even be able to approve or reject, and, even more, pay only upon approval -- but the only functionality I absolutely need is a secure login and client-specific downloading.

THANKS!!