I am planning these for my new system: ASRock Z68 Extreme 4 Intel i7 2600K Gigabyte GTX560 Ti OC 8G DDR3 2TB HDD I'll use it for playing old games (2-3 yrs ago) and editing video. Is a 550W psu sufficient? Or I need to go for 600W/ 700W?
check my specs, running a similar setup. No problems with a 650 watt psu. if you only want it for a couple years then get a 650, if you want to keep it through your next few years after that. Go for a 750, that will allow you to add another card and over-clock.
550W is perfectly fine. Matter of fact 500W is fine as well! My system under 90% load uses a max of around 375W.