Multi Vendor Marketplace developer with Experience need information

I am looking to build a multi-vendor marketplace website. I can provide more details later but basically vendors should be able to signup and sell directly on the site and manage their sales from their own login. I am looking for providers who have built such a website to engage with them for consulting and provision of same. I do not mind if the software is based on magento, or opencart or some other shopping cart software as long as it is fast. I would prefer not to base it on magento as it need a lot of hardware to run it fast. Please only experienced developers contact me, please send me an email detailing: 1. If you have built a marketplace before. 2. If you built from cratch or used an exisitng platform osc etc... 3. URLs Please do not send me a list of useless sites, I am only interested in actual multi vendor marketplaces. It cost me $28 to post this ad here, so please be serious and professional, and please do not waste my time by sending me a list of basic websites. Please note this bid is not final as the specs are not here, a cost can be worked out later with the provider. I'm looking first to engage with a provider to see what they can provide. Thank you.