Get a sapphire ati radeon X800GTO2 and unlock the pipes to 16/6, it's the same core as X850XT. I've heard that some connect3d X800GTO cards should be able to unlock as well
Na the sapphire card X800GTO2 is at the moment 100% that it could be unlocked, it's only bios locked at the moment. I'm not really sure about the connect3d card because it's new. But on the page where i read it had they succeded with 3/3 cards