I am not familiar with InfusionSoft, so I cannot speak to that. But for the membership levels, Organic Groups (http://drupal.org/project/og) might be your best bet.

Nancy

From: Sam Barraclough
For example, a customer purchases our Bronze Membership. They can only access content on our Drupal site that we have created for Bronze Members.

Does Drupal have the capability to differentiate our customers based on membership level and control our content release accordingly?

And where possible we would like to link this in with InfusionSoft API module.