I read your project description, and i understand your needs. I have over 10 years of experience with PHP/MySQL, Linux/Apache/PHP/MySQL administration, also strong knowledge of Magento and past experience with similar projects. However i need to know more information about your hosting (shared, virtual server, private server), because i can achieve significant speed up only if you have virtual or private server (on share hosting isn't usually possible install php extension, and tune apache and mysql services). If you have additional information (for example URL could help) or some question, don't hesitate to post them by PM, thanks. I'll reply in no time with more information about what can i do for you.