wordpress for an ecommerce site? I know there are shopping cart plugins for wordpress, but wouldn't I find myself shoehorning and work-arounding everything, rather than a solution that's built for ecommerce?
ShopSite will can clean URLs as can many others. The level of effort required to make it happen varies widely. Research on the forums for the carts you're interested in and you'll learn quickly what it takes to make it happen or if it's native to the core code.
I would suggest against the idea of having a category name as part of the product URL. Its a very old way of thinking because a product can belong in multiple categories. Your money page should just be product name. The navigation can vary that leads to the money -- which can have the category name in the URL.
Sorry I don't have specific recommendations for you.