I have decided to go for a new computer with Intel C2D. However i am looking for a motherboard / chipset that is well known for its compatibility with linux. So if you can help me pointing out to a linux (RH, gentoo) compatible motherboard it would be really helpful
Welcome to the forums! :)
I think pretty much all of them are now compatible with Linux. It seems to me that some network controller chipsets have a few issues now and then, though.
Not sure if it's totally true, but I read here that Linux now supports more devices than any other operating system:
How Linux Supports More Devices Than Any Other OS, Ever - O'Reilly Broadcast
Best of luck with your efforts.