Well it's going to take up alot of space storing all that in Subversion, I'll tell you that much. Subversion doesn't store binary files via delta's the way that it stores text files. It'll probably take up as much space as it would to just store a bunch of binary files on your hard drive, plus the repository.
You may be able to a server-side tiddlywiki to store the urls to the documents within Subversion.
If they are mostly .doc and .xls files, there's also Microsoft's Sharepoint.
