The peeps over at Lowyat Hardware QnA forum asked me to help contribute on rig suggestions for various budgets, mostly for gaming since this is what most of the requests are usually for. So, this is my personal opinion. So don't need to flame me yeah! CnC is also welcomed!
Mostly gaming rigs, that is prioritizing graphics card over other components first, then only the other parts =)
And ohhh, some might be asking, is 500W really enough? Answer is YES. Modern graphics cards nowadays (2011/2012) uses a lot less power compared to years before, usually in the range of 200-250W at maximum. With the other components, total system consumption is usually less than 400W. So a 500W PSU is sufficiently enough for a single GPU setup. Would be good to have a good 150-200W 'headroom' as it's better to not have PSU to have high load all the time
However if you're into stuff like overclocking your CPU to the max, it may not be enough.
Credits to Tomshardware: http://www.tomshardware.com/reviews/geforce-gtx-670-test-review,3217-15.html