Ordering / Checkout system for website

I would like a checkout process just like this one here: [login to view URL];spid=VQOZZZ&signup=true&sbid=dKTFH&cids=ZZ34TZ,0&spids=VQOZZZ,71&spoptid=71 (See each step of ordering, paypal, credit card separate, etc.) There also is an admin area showing the pending orders, cancellations, shipments to send, etc. I know there are man shopping carts out there and will make a preference for a bidder who can show me an existing shopping cart that you will just install on our server (and/or customize) to make it just like this process. Thank you.