Not sure if 6950's are supposed to run hotter..
But my Sapphire HD6970 (stock volts, stock clocks) on iddle is at 36-40ºC on AUTO fan, which is at 25% (minimum).
Maybe it's just because of it being an HD6970, or maybe because I have a great air cooling case.
But I find 51ºC iddle a bit too high for auto fan.