Business directory with custom retailers lists

We need customized business directory of retailers, something like Mosets tree with support for site users to create and manage lists of retailers; front-end and back-end should fit descriptions as defined at attached specs; very important - no more steps to follow except defined at specs, and no difference or very minor difference with the interface (design will be developed and implemented as template outside of this project). With your bid pls let us know if you can modify any existing FOSS solutions to fit our needs (i.e. Joomla+Mtree) or create the soluton we need from scratch (if you can do both, pls provide price for both cases). On budget - lower bid will have better chances to win, but more work on this project will be outsourced in the future.