[NAME]     I don't trust Ebay nor amazon for electronical components.        check your local Best Buy if you don't like purchasing online . . . but both Amazon and eBay have excellent return policies. Seasonic Focus 750 watt    . . . you should look for something with these dimensions:  140 mm (L) x 150 mm (W) x 86 mm (H)
I have gotten an Alienware Aurora R5 Desktop around 4 years ago. Very recently within the last two weeks or so, the PSU fan has started acting weird. When no intensive programs are running or during startup, the PSU fan will rev up every 10 seconds for about 1 or 2 seconds then go back down to its normal speed. The weirdest part about the fan is that when running CPU and GPU intensive games such as Mordhau and Arma, the PSU fan will start acting normal. I am running windows 10 and on Alienware bios version 1.0.23
Aurora R5, PSU fan problem