71C at idle is pretty extreme, is there enough airflow? Before you drop a few hundred on a custom loop for your cards, experiment with some different airflow schemes. Even if you go water, you'll still need to blow cool air across the radiator.
A bad work unit took me down 12 places yesterday. I'm digging up an old video card to try to fold on two GPUs at once to compensate.
This is my first time "competing". I gotta say, folding is much more fun when its a race.