What are your requirements? If you've got some Linux expertise in-house, do you need the Entrerprise cover from RedHat, or would a standard distribution do?
As for Win2K3, that depends what kind of future you're talking about. It's got more of a future than Win2K, but less of a future than Win2K4/5/6.
You have to buy something at some point, and that will eventually go out of cover, but that's life.
I don't understand why you balk about a $300 licence from RedHat, but still consider Win2K3, which has a base
price of $999!