How to setup a shop like wpmudev.org? Using Membership & MarketPress?

Hi,

I need to setup a shop to sell software components and templates (similar to wpmudev.org but not for wordpress) with the following requirements:
+ Visitors (non-members) to the site can purchase individual components for a price or subscribe to become a member.
+ There are 3 membership levels: Free, Standard, Pro. The Free and Standard membership level have limitations on which components they're allowed to download, but they can purchase the other components (optionally with a discount)
+ We also need to have a support/QA system for the members.

I'm thinking of using the MarketPress plugin for the product management and ecommerce, Membership plugin for membership management, and Support plugin for support/QA management, with potentially some custom work to integrate them.

These features are similar to the ones implemented at wpmudev.org. Can you guys share or give me advice/directions on how you implemented those features at wpmudev.org? Which plugins are you using and how much custom work needed to make those plugins work together as smoothly as it is at wpmudev.org?

Thanks.