Does anyone know of a good mp3 player that will be compatible with Windows Media Player?

I want to buy an ipod, but all my downloaded/ uploaded music is currently on Windows Media Player and switching it all over to itunes sounds like it will be a hle. Does anyone know of a few mp3 players that are compatible with WMP and comparable with an ipod? something around 4-8GB (more so the lower end). Price isn't really that big of a problem for me. No more than $200, but the less expensive the better. Thanks