Web application to manage subscription services

We wish to develop a professional web application to configure and manage subscription-based access to a suite of xml web services. The web application will not provide the actual xml web services, which are being developed separately, but it will interact with them for subscriber validation and usage logging. We are willing to consider various programming languages and platforms, but we plan to deploy and run this on a linux system. PHP, Java and Ruby solutions will probably be the most attractive to us. We are seeking a solution that powers a self-service website which lets people: * sign up for free or paid accounts * view and agree to terms of service * select and configure service options * enter payment credentials * edit their account and billing profiles * review their service usage and billing history * request reports on their service usage and billing history * suspend or cancel their accounts * invite others to sign up using a personalized affliate link From an admin perspective, we would also like the system to let us: * monitor and manage service status * log user activity and service consumption * review and manage user accounts * manage recurring billing, flag problem accounts * manage account credits for affiliate signups * manage credit and quota adjustments on user accounts * manage message templates for communicating with users * configure service packages, options and discount codes * produce reports on user accounts, billing and service status * perform other fundamental administrative activities The xml web service will need to access this system to: * check the validity of subscriber credentials * check whether subscriber is entitled to use the xml web service * check whether subscriber is over quota for service usage * log subscriber usage of the service * handle errors and relay info about them to user and/or admin It is acceptable to use existing open source components to assemble this solution, but we must approve the use of any such components in advance. All development work will be confidential, and developer will be required to execute an NDA. When complete, all ownership rights and title to this solution will belong to us, and the developer must guarantee not to develop a similar or competing solution. Only developers with a proven track record of on-time, on-budget success in serious, professional projects will be considered. If this project goes well, then there is a high probability of significant follow-up work.