Need to move to lates shopping cart

I need to upgrade to a brand new shopping cart which has all the bells and whistles. I already have a successful running website for last 6 years. Currently I am using Creloaded (OScommerce) on which I have installed and configured several mods (SEOURL,etc) and deployed myself on Cloud VPS and CDN. But after 6 years on same platform, I feel I am getting "dragged" by it now as I see much nicer shopping out there with amazing front end. At a high level new site should have: • Front end built on HTML5 boilerplate • Responsive Design (mobile, desktops, etc) • opensource - preferable LAMP architechture • framework which is extensible with addons • SEO freindly - I am using OScommerce SEOURL mod and must maintain URL's From the front-end perspective I would like to base my design on a particular site (will share details in PM) that I have in mind. I have done some research already and I really like the roadmaps for OSCommerce 3.1 and Loaded 7 (Crealoade 7.0) but seems it will take some time to get in the market. Also looked at magento and prestashop but not sure if they meet ALL of my requirements. Therefore, I wanted to see what the expert are saying and whether they have better idea than what I had in mind. I can share much more in details of what my requirements are and the examples of the target websites. I need solution providers that can: • Share your past experiences and work. • Consult and advise on making decision on choosing right solution • Provide feedback on my examples and ideas • Be available for chat or conference meeting I can even pay for consulting if the information is valuable.