What makes me best for this project is I work with WooCommerce daily, I've previously worked for WooThemes in WooCommerce support doing this exact thing daily, and am a core contributor to the plugin itself.
[login to view URL]
The biggest issue you are going to have for performance is your hosting environment, no one can guarantee the speed increases you are hoping for with the size of database you have. If you are on a shared hosting account that is your problem, for $30 I can setup a VPS for you that will run your site much faster and I'll migrate your site to the VPS.
You will of course be responsible for the cost of the VPS hosting each month, I'd suggest a 1GB linode VPS which is $20/mo.