Team / Seller profile/widget with URL

I´m looking for a plugin or solution that can be used by my company.

I would like it if my team of sellers could refer the potential clients to a specific URL personalized for that seller.

i.e.

http://sellername.mydomain.com/
or
http://mydomain.com/seller/name

depending on what url is used it would generate a personal widget with the profile and contactinformation for that particular seller. And if no refferer url was used it would generate a company profile.

The plugin would have to work regardless of what subpage the client is visiting. ie

http://sellername.mydomain.com/productshowcase
http://mydomain.com/productshowcase/seller/name

The workaround to this would of course be to have multiple installations of WP and have been used before, but I hope for a better solution.

Any ideas?