Renaming Files in Finder

I would like to quickly rename about 200 files in finder. They are video files and have names like "Watch-OnePiece.com_219" Each one is numbered and I wish to rename them with just the number (in this case 219) Can you tell me how to do this without manually changing each of them?

Thanks

FileBuddy lets you delete characters (say all upper and lower case letters

It doesn't state 10.5 compatible but you could always give the demo a try

also not 10.5 but may work, it's free too, and very good.

renamer4mac