it makes very little difference in installing the PSU fan face up or down. the biggest issue is keeping dust out of the PSU and with the 500R you have a filter on the bottom for the PSU fan. Most modern cases now have vents for the PSU with the fan face down. For years the antec gaming cases had you install the PSU fan face up and had great air flow. Makes little difference but like I said, dust can be an issue in the PSU.