This has been done for quite some time. I have a Compaq P75 machine(I dont know if I should be admitting to that) that runs the fan slowly and makes almost no noise. I also have another PSU that uses a NTC resistor to vary the speed of the fan based on the temperature on the air inside the case. This would probably be the best way so that the fan would run at full speed if it was a hot day and the player heated up. I believe a circuit to do this was published in one of the Australian electronics magazines(either Silicon Chip or Electronics Australia) I'll see if I can dig up an old copy out of my collection.