write a set of technical requirements for an online marketplace portal

I am in the process of writing a proposal for a web development firm and I am stuck with the technical requirements section. I have all my ideas and sketchs documented, however, I want to transform my ideas and things that I want the website to do such as ( rating systmen for sellers and buyers, award system for frequent buyers, referal system to get more sellers (traffic) into my website, real time auction, online stores, etc). I will disscuss all my ideas with whomever wins my project so we can transform everything into a set of technical requirements and this is important because of two main things : 1) to get an accurate quotation/ price from the web development firm. 2) determine the scope and size of the project. The project will be build using Drupal with some PHP customization. The first step of the project will be to build the user experiance or in other words information architechture (IA).