WordPress with Download and Support Area

Hi,

I would like to sue WP as our new CMS for our website instead of Typo3. All is fine for the content, BUT:

We offer our products as download for our customers. But not every customer can download every product and version. So what I am looking for is a plugin/feature in WP which allows us to

– create frontend user groups (in addition to the 5 built-in groups
– manage the groups
– manage users inside the groups (if possible also with self-registration, but this is not a must-have
– manage access rights to certain download files based on groups
– offer a simple overview page for the user to see what he can download (and maybe even what would be there if he was in another group(=paid more)

I searched a lot, but could find anything suitable. WordPress Download Codes was nice, but couldn’t quite give me what I need.

Any ideas? HAs someone built something like this before?