Not sure you followed justperry's post...
If you have a library that is too big to fit on one disk (I have this very problem), you can load files all into iTunes from many sources/disks with no issues. The key to making that work though is that you have to turn off a preference in itunes that states something along the lines of "copy all media to your itunes folder". By turning this off, it leaves all the files in their original locations and doesn't try to copy it all to one disk. In my case, I have all of my Music on one hard drive, all of my movies on a second hard drive, and all of my television shows on a third hard drive. If I left the "copy all..." turned on, it would try to copy all of the media from those three hard drives to one single hard drive and run out of space. By turning it off, iTunes just reads everything from whatever drive they are on. When I go to my AppleTV, it just sees all the files as loaded into iTunes and it doesn't care whether it is coming from Disk 1, 2 or 3. It's all seemless.
You have to use iTunes and Homesharing if you want to read files from your local network (maybe that's the misunderstanding here?).