ecommerce website

I have a good market contacts and one marketing guy working for me, currently we are engaged in old stock clearance, like companies having old stock, I contact them and engage buyers to purchase that old stock, get a commission on that. My brother is already running a stock lot shop in Karachi which helps me on garment stuff. am planning to have a website (paid service) for the companies, where I'll offer my contacts( companies) to register their stock (old/clearance/off price stock) on my website, on the other hand buyers will visit the site , view products and make their offers/bids for this bulk stock. Here is a website, which is doing the same but they are putting only the stock which is available with them, I need to make it open for all people who will create account on my website. I would request you to please have a look on it and let me know the quotation for development, shopping cart, 2CO configuration will be [login to view URL] may use OScommerce. pls have a look on below website, I need this sort of thing.