AMD recommends 650 for 6800 and 750 for 6800 XT. But these recommendations are usually above what one really needs. In reality, it will depend on a particular PSU and the rest of the hardware, and there's hardly any way to tell in advance. The only reliable way is to actually try it. With that recommendations, I'd think 600 should be enough for The article claims that a typical fit cyclist might be able to crank out 250 to 300 watts as an average for a 20 minute FTP (functional threshold point) test, but that’s not the case. In fact, according to the article, the average power output of a cyclist is only about 100 watts. That’s a lot less than the 250-300 watts claimed by the A: A gas fired, forced air home furnace typically requires a small amount of electricity to ignite and operate in your home. Most gas heat furnaces use less than 600 watts of electricity, or less than half of a typical 15 amp electric circuit. The gas furnace uses this small amount of electricity to power the blower or fan part of the furnace The 800 Watt PSU would run at 62.5% of max rating. That is a good value. The 1200 Watt PSU would run at only 41% of its maximum rating. That is still within the normally accepted range, but at the low end. If your system is not going to change than the 800 Watt PSU is the better choice. .

is 600 watts a lot