Let’s say that you are buying a “Sapphire AMD Radeon R9 280X OC VAPOR-X” video card which has 3 GB GDDR 5.
However, since the video card is very powerful, you don’t want to run your video card on a cheap no-brand power source.
An optimal power source for this video card can be a “Sirtec – High Power Element BRONZE 600W”.
600W should be more than enough. Plus a good brand power source will assure you that the power is provided and not missing.
Such power source costs around 50 euro or around 60 dollars.
If your budget allows it, you can go for even a better power source with better specs but you should consider at least the “Sirtec – High Power Element BRONZE 600W” as minimum for your new video card.