Build an addition to our website

We already have a website. We now want to grow that website into the next stage. The store will have a xml data feed from our supplier. The store will have the following features. Ability for us to create computers with all the periferals of that PC, it will use the Case as the display photo of the system, it will calculate the system price wholesale and allow us to set the recommended price then publish it to the website. Their will be categories of systems and we can build systems for any categories. We can also edit, add, change or delete categories Example.. Home & Student Business Gamer As well as our pre build systems that we will configure in this area, we will have a PC parts picker where users can customer their own systems. As well as the system builds displaying in the store All our parts will also be available for purchase that is in the datafeed, all broken down into their respective categories and pricing. The store will be clean, simple to navigate especially for mobile and tablet. Will have all the features of cart, checkout etc will have the same look as feel of the current website so it doesn't look too different. Please look at the attached file which is our competitors website. I want what he has but it to be better and not so manual in the back end. Example we can pick parts, it lists them parts in the description and adds the photo of the case we chose for that build along with a price. Our website is [login to view URL] Please note this is not to build a complete new website, this is an addition to our website.