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chrissto, it sounds very much like a job, XOOPS can take.
The latest version of News can handle attachments - but I don't know if you are more after displaying white papers etc.
Most sites have a forum, but e.g. www.gaining-mass.com has a news-oriented approach.
I also know that there is an osCommerce module for XOOPS, but as I haven't tried it, I cannot say how easy or difficult it is to use.
Generally, modules use Smarty Templates for the presentation part, with quite extensive use of CSS.