Clone an ecommerce website

Want an ecommerce website to sell gadgets. I looked around, and want something like [login to view URL] (in terms of UI), and want a site that supports the following - UI similar to [login to view URL] - Has inventory management, shopping cart etc. - Linked to Google Checkout or some other payment system - Also, has an account associated with each user, to view order history and maybe offer some points etc. - Should have a admin mode as well to look at order history, and provide stock reports, sales figures, etc. - Support for discounts on a per category/product level - Should be able to customize the various category hierarchies and also the current promotions in an easy way. - Should be scalable to support 1000s of transactions a day - Also want code to be written in a way such that the UI can easily be customized later (separation between UI and data layer) Looking for a solution asap. Please contact asap to discuss in more detail.