File Managment: Approaches?

Hello everybody,

I have been looking into a way to manage my files across drupal, but somehow I can't get it quite right. What I would like to be able to do is this:

• Share Files across nodes - No "double"-Uploads.
• Restrict Access - with the copyright law nowadays I would like to be able to: Restrict directory access based with an individual password or/and based upon IP range detection.

This requires of course a file tree somehow and a way to attach nodes. Right now I am using webfm (drupal.org/project/webfm) and ICME (as an integration for fckeditor, drupal.org/project/imce, drupal.org/project/fckeditor).
This leaves me with some problems: No access restriction and a little hassle about "seeing" and indexing the files between webfm and ICME.

No I am wondering how everybody else solved this?

I noticed someone using cck-fields to export things from ICME, but I mainly would like to provide Presentations (PPt,Impress,Flash) and pdfs for download.