NAS For file server and storage?

Here's my sitch that no one is able to figure out for me. I operate a small business where several graphic files such as tiffs, eps, quark, adobe files are located. They are currently on an Imac that is acting as our server but we're running out of space and need to move the files to a device like a NAS. The problem I'm running into is that thousands of files have file names that will not move or copy to any PC based NAS such as Buffaloe, Seagate, etc. It doesn't like back slash or forward slash, etc etc. I was told FAT32 is the problem. So my question is there anyone out there who has a solution? Can these NAS devices be reformatted easily to MACOS? Or...? HELP!