Ok, so OSS is basically not an option for a 7970 right now. I'm definitely not going to sell it for a 6XXX card, as that makes no sense whatsoever. I guess I'll just go back to fglrx until the driver progresses. It's times like this I wish I was a better programmer and able to help. Thank you for your patience.
Thats a good decision. Using nvidia would however also be possible path, but only if you use closed source. It'll have much better wine support, faster 3d, better power management, better video acceleration; however weaker hardware (in terms of compute), worse opensource support, worse multiscreen support.