e-Commerce Plugin with Specific Cababilities

Hey,

I’m looking for an e-Commerce plugin for WP that can do some very specific things. I need to be able to cross-sell some addon products, and I’ve been asked to either do it all on the main product page or in a wizard-type situation.

The all-one-page system would have the main product, a quantity field for that product, then several addon product names with quantity fields for them, and finally an add to cart or buy now button that would add the whole deal to the shopping cart. It would be nice to have the ability to restrict addon products based on which other addons are selected, (so if you get addon A you cannot buy addon B but you can buy addon C and D).

Alternately a wizard would work: Select the main product, then select an addon on the next screen, then select addons that are only available with the selected original addon on the final screen.

I’ve been developing using WP e-Commerce, but it turns out that it’s very hard to make something like this work with WPEC, and I’m wondering if it’ll be easier to find another shopping cart system that has this kind of functionality built in.