Dental Deal - Reverse Auction Website PHP

The site is meant to attract patients and dentists. Patients can initiate reversed auctions by posting their dentists' quote for the proposed treatment (e.g. crown or implant etc.). Registered dentists may then respond to the initial price for the duration of the auction. There will also be some kind of external payment gateway for billing. Price charged to patients depends on the price range of the treatment. The site should also allow for an assessment functionality that allows patients to see other patients' comments/ratings for previous treatment. We are looking for someone that will - help us to determine a proper CMS (open source preferred) for a revised auction system and external gateway payment provider - has elegantly developed similar projects in PHP - will customisation of the CMS and code additional modules if required - has attention to detail and documents code efficiently Knowledge of web design may be advantageous. The web-site is going to have a dental touch.