I only use the 6970 which is not overclocked.
It gets up to 80 °C.
Now I'm back to the 6850 OCed to 940 MhZ which runs at a steady 250 Mh/s. The 6970 is three times as loud as the 6850. I never heard anything like that.
They do get loud. That cooler is expensive but it should do a much better job and be quieter. Be sure you have to room because it adds almost 2 inches to the length. Here's the comments for it from newegg.http://www.newegg.com/Product/Product.aspx?Item=N82E16835186043&Tpk=6970%20cooler
I'd get MSI Afterburner and lower the memory clock speed and use manual fan control. See if you can run it at 50% under-clocking the memory. Also use -f60/-f166/-f266 to slow it down to keep the temp down. You might be able to under-clock it and still get 350m/s without it sounding like a jet engine.
You can probably even use -f500 to reduce the gpu load to 70-80% and run the fan at 40%. 80C sounds really hot for just 1 card in a system. I run 3 of them and the bottom one which gets the best airflow runs at 63C under full load with the fan at 60% (400 mhs). I could easily underclock that to 350 mhs and probably have the fan at 40%.
If your fan is running 60-80% and still 80C you have an airflow problem if it's a single card setup.