I need to replace a power supply, that has become very noisy, on a DELL optiplex 755. I have a DELL optiplex 745 on hand, that has a good power supply. They both have the same sized chassis, 'desktop' size. Do you think it is safe to replace with the power supply from the 745 or would you order a new part from DELL. It is a very important PC. The replacement part I found online says 280 watt. Please let me know what you think.