I'm looking for a good shopping cart script that supports the ability to ship to multiple addresses AND runs on Unix/Linux. This needs to be built into the cart's shipping calculations, not just a textbox where you can specify additional addresses because the UPS or FedEx API needs to calculate the shipping based on multiple addresses and each one's ship to address independently.

Of course I'd like it to have other options as well, such as upsell, cross-sell, gift certificates, quantity discounts, etc.

I've been looking at Storefront (storefront.net), but I prefer a non Windows-based script if possible.

Anyone have any good suggestions?

Thanks a bunch!