Members subscriptions

Hi All,
New the forum, i have been using wp for a while and at the moment i am creating a site for a client that needed a custom registration page for members to join, i then created a scroth that pulls some of the details from that custom registration page (wp-register.php) that populates a searchable map, but my question is the client wants another section where he wants people to be able to sign up not as a member but as lets say a company and allow them to advertise on the site for 3, 6 and 12months all which will have different prices like subscriptions, i have tried some of the subscriptions plugins but all interfer with the wp-register page already in place, can someone advise me as to a plugin or a hack that can accomplish this without interfering with the custom registration page (wp-register.php) i have already in place for member sign up.

any help would be great