I need a wordpress shopping cart that will produce 2 tier product variations. For example if you pick 'option 1' for a product, sub-options 'x' 'y' 'z' will be revealed and if you pick 'option 2', sub-options 'a' 'b' 'c' will be revealed. Im OK with a commercial cart, but I haven't found any that specifically list this functionality in their documentation and since they are commercial, I can't access their respective support forums to find out more with out first purchasing the cart. Is there a cart that supports this kind of functionality?
The e-commerce plugin Shopp for Wordpress seems to allow 2-tier product variation options. It used to be a bit buggy in the 2-tier product variation department, but I think that they've fixed those issues with the plugin now.
Keep in mind that Shopp isn't free, but in my opinion it's worth every dollar. MarketPress is supposedly going to support this as well, but WPMU Dev might take a while to release a new version of it.