Shopping cart development (Customized)

We have designed a shopping cart mockup that we would like to be coded/implemented, now. While most of the pages are usual shopping cart pages, the product detailed page + Checkout pages will need some customization. Basically, we would need to the ability for customers to enter multiple product quantities based upon color and size selection. The cart should be able to automatically add the quantities for each product individually and still be able to maintain the matrix details (how many quantity of what size and which color etc). So, instead of customers going back and forth to select quantity, color and size, we want it to be done easily at one place. The pricing module will need customization too. We need a module where we can upload upto 5 different prices - prices will vary as per the total quantity. for eg: $5 per piece for more than 10 pieces $4.85 per piece for more than 30 pieces $4.50 per piece for more than 50 pieces $4.25 per piece for more than 75 pieces $4 per piece for more than 100 pieces. At the backend, we would need the ability to upload a CSV with all the product details, pricing and attributes, and images names/path - pretty much like any other shopping cart. Please have a look at the attached file before making your bids. Thanks.