"Enterprise level" e-commerce software (online mall)?

Hello everyone,

I'm looking for a good shopping mall program, but haven't seen one that does everything I need. I've been using osCommerce, but the site has grown and we need many features that OSC doesn't have (nor are there contributions for them). Though OSC can be modified to achieve most of them, the time, cost and loss in reliability wouldn't be worth it. I'd love to find a commercial solution that is rock solid and backed by good customer service. I've looked at X-Cart Pro, Storefront, eBay Pro Stores, Miva, etc., but none fit the bill out of the box.

I'd appreciate any suggestions you folks might have. I'd like to avoid having this written from scratch, if possible.

My goal is to set up an online marketplace in which members/vendors can register and setup their own 'stores' within the mall and upload product images and descriptions via a web interface, similar to how eBay works for sellers. The main mall portion of the site will serve as a marketplace where we simply host vendors' stores and do not process any payments or orders (as they are sent directly to vendors). However, we'll also have a section of the site in which we will sell products ourselves - for this, we would process all aspects of the transactions.

Here's a summary of the main features required:

1. Individual subdomain names for each vendor (e.g. "www.ourmall.com/vendor_1/")

2. Ability to handle large numbers of products and vendors (upwards of 100,000 items, 5,000+ vendors)

3. Vendors are paid by customers directly, instead of having payments go to us (the mall owner). For example, each payment would be sent directly to the applicable vendor's Paypal account or processed through their own credit card gateway (if they have one), as with eBay.

4. Vendors are billed for a transaction fee (% of each sale).

5. Vendors can establish their own shipping rates and terms, based on weight, per item, by zone, or other means.

6. A vendor feedback rating system, similar to eBay's.

7. A messaging system through which buyers and sellers can communicate with each other directly (like eBay's "My Messages" system). Messages forwarded to email.

8. Ability to create a variety of store templates from which vendors can choose.

9. Ability to auto-bill each vendor for a recurringmonthly hosting fee.

10. Ability for vendors to create discount coupon codes, free shipping offers, etc. redeemable on their products.

11. Extensive web-based store management interface, with functions similar to eBay's seller interface. For example:

Orders received
Order status
Inventory status
Shipping status
Tracking details
Shipping options
Coupon codes
Feedback status
etc.
Various alerts (e.g. send invoice, mark as paid, etc.)

Thanks in advance for any suggestions!