I have the same Dell power supply as in the photo, and I run it at low fan speed with two overclocked S1. Which will work, but will cause the power supply to overheat and trip thermal shutdown. If you can bear the jet like noise, the power supply should be able to cope with to S1 even overclocked. Since these power supply seems to be built with top quality parts. (they ARE server grade power afterall)
If you do not overclock, I think it should work fine with the power supply fan staying in low speed mode. I just went ahead and got myself a larger power supply, and have the fan run in quiet mode, as not to drive me and my family nuts..
