It's a difficult choice and it must be made VERY carefully as once you go down a path it is difficult and costly to change. Make sure to do your due dilligence, asking lots of questions like what file types, what languages, connection speeds, etc... (there are actually too many to mention here).
EPDM does work very well as a worldwide application for CAD data management. The largest install I have managed has been an 8 site company, 7 spread across the US & one office in India and it performed well.
Hope this help.
EPDM can handle this. And can manage you Inventor and Pro-E documents. Simple use of Archive and replication servers.