I just happened across a forum post where LM741C decided to try and run his Nvidia GTX-580 with the Danger Den block on a single 120mm SR-1 radiator.  His goal was for silence.  The DDC pump was run at different voltages as well as the single fan. The results are very intersting.  Able to maintain temperatures in the 60's with reduce fan and pump voltages!!!

Check out the entire post.