PHP Shopping cart recommendation?

I don't know if I am posting this in the right forum, but here it goes. I am looking for a PHP, Mysql shopping cart that is able to do the following.

I have set up PhpAutoMembersarea to set up a secure members area and sign up, for wholesale customers on our website. There is also a public area for the general public. what I want to do is set up a simple shopping cart on the secure part, so wholesale customers can shop, pick what they want and then check out with no payment terms and shipping, so we will just get their basic order minus shipping and payment method. We want to be able to negotiate these terms with wholesale customers after they have sent us an order. On the flip side I want to be able to have the public shopping cart with a shipping modual(ups) and credit card processing if possible, all run from MySQL with templates. Am I dreaming? Can anyone recommend a half decent cart script that is either free or costs very little as we are just starting up. Most of them I have found also include sutomers managemt and sign up moduls as well. Hopefully this all makes sense.