iTunes and file format

I have several computers -- both Macs and PCs -- and am looking to finally consolidate things. Current music server is a (Vista) PC with library on external drive formatted in NTFS. I know this will work if I plug it into a Mac -- I've tried it -- but can I then just go ahead and import new CDs using iTunes on the Mac without making any changes to the external drive? Or is there a better way to do this, some other file format that would make more sense for a Mac-based server? If so, can I copy what I've got onto a properly formatted drive? (I sure as heck don't want to rip all 659 discs again!) I really don't know much about all of this -- as is doubtless obvious from this post -- and I'd really appreciate any help you all could give me. Thanks so much.
Howard