If you want absolute control, there are tons of starter carts available. Most will allow you to host them yourself and some are easily modified.
I use VPASP. The starter pack is free, quite comprehensive and easily modified without scripting in ASP. There are custom skins available for purchase and several developers whom you can contract for initial setup and customizations.
At any rate, it's an inexpensive solution regardless of whether or not you opt for the basic or full packages.
Check it out:
Shopping Cart Software – Ecommerce Solutions and Web Hosting From VP-ASP
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