What non windows shopping cart handles multiple drop ship vendors and is SEO

[WebGuySurfing]

friendly? I need to find a shopping cart that is hosted on linux/apache (Non windows). The source code should not be encrypted (editable and PHP preferred). The cart must handle multiple vendors or drop shippers (allow purchase from multiple vendors, while looking like one store, yet calculate the individual shipping charges. For an example see X-Cart Pro's features at http://www.x-cart.com/pro_features.html). It should use CSS templates and provide for SEO friendly URL's and metatags, etc. These features can be built-in or available thru modules, plugins, etc. I have seen X-Cart Pro and am looking for alternatives to it.