I made a thread earlier to help me find an upgrade for my PC to improve FPS and was advised to get a new video card which I chose to do. However, the video card I want requires 400W but I currently only have 300 so now I need help finding a power supply compatible for my computer.
no, see what manufacturers have to do is put the top end of wattage of their cards down SYSTEM wise. The twp of a 7770 is only 106W. Your system has a 300W power supply, and a 2 rail 12V system. The first rail (8A) is just for the cpu, and the 2nd rail (14A) is for the rest of your system. MAX draw would be 106W, your secondary rail will be pushing out the MAX of 168W (to get that you multiply 14A times 12V so 14x12=168) so you have a 62W margin (more then enough to run your hard drives, usb ports and everything) if you have you cpu and gpu running at 100%. Hope that helps.