The latest BIOS for your 755 is A22. Best CPU for it is C2Q Q9650 3.0Ghz. Some compatible GPU's: [IMAGE] No need to upgrade PSU with those options.  Upgrading it is somewhat difficult for a DT. I'm going to suggest have at least 8GB for Win10.  It'll work faster. With the options I gave, that 755 will fly, and that doesn't even include a GPU card.  I used to have a 755 MT.  Oh yah, and don't forget the SSD.
Hello, I have an older Dell Optiplex 755 DT, and I want to transform it into a retro gaming machine. I figured this older system would be good to do it with. I had a modded Nintendo Wii I played retro games on, but I no longer own it. I also want to browse the web occasionally like watching YouTube videos and checking things like discord and Gmail. I currently have an Intel Core 2 Duo E6550, 4GB of ddr2 memory and no GPU. Anyways I am here to ask if the PSU would need to be upgraded if I were to upgrade to a Core 2 Quad. I also want to add a GPU which Is why this is a concern. Does anyone know what GPU and Quad Core CPU I can use for this system? CPU seems to handle well, but I believe it would change once it’s online. With it disconnected, it uses about 1GB of memory, but that and an SSD is not what I worry for, this is just a project and I know this system probably shouldn’t have any money put towards it but eh. Ill replace the thermal paste with arctic mx4, and I’ll find the latest bios driver, although I believe I’m on the latest version.  EDIT: the psu inside my system states that it has an Input of 100-240 volts and a DC output of 280 watts 
Dell Optiplex 755 DT