I've changed the stock one on my A4000 psu to a Verax model that's thermally controled through a sensor.
I must admit that the air flow is terrible :-o but then again if I put my hand over the PSU it's cool so probably the temperature just hasn't raised enouph for the thermal sensor to raise the fan's rpm.
The fan was developed for cooling of PC houses so I take it that it's more than adequate (e.g. comparing a high temperature inside a PC case and inside a PSU, it's obvious that the 1st case would be much more harmfull cause that would imply the motherboard and component's temperature was even higher).
The fan I got was
THIS one BTW.
