Xtwargodtx :
See the thing is Zenx the VS650 is an older power supply and wont be able to run a r9 270x so
With all due respect I disagree
First of all there is no such thing as a '50w rail', the power supply is rated at 650w which is more than enough to run the card that requires a maximum of 150w (the r9) provided it has 2x6 pin connectors you can actually connect to it... and it actually has them so it's not that old in the first place.
The way you would calculate it is to add up the maximum power consumption of all components in the system (which for his system would be actually less than 500w) and anything above that can run it at full capacity without any problems.
Furthermore the sapphire website also mentions this under system requirements that you would need a 500w psu (they calculate this by adding the 150w required by the card itself to a pretty heavily loaded imaginary system's consumption)
http://www.sapphiretech.com/presentation/product/product_index.aspx?pid=2038&lid=1#
It also mentions that even a 600w psu is enough to run TWO of these cards in crossfire... so nooooo I seriously do not agree
The only requirements for the PSU would be to be compatible with your system (have the required connectors) and to put out stable power (which is why people usually go for brand names rather than no-name psu-s which come with cheap cases and yes corsair is a reliable brand in that regard) the wattage simply depends on your system consumption, and no your system won't get any better at all.. not even by a fraction if you replace a 650w psu with a 750w psu if your consumption is already below 500w
I really mean no offense by this buy I really disagree with advising people to spend money as a first option... that would be rather a last resort... I mean that's why people actually bother to check out this site... otherwise they could just spend money hiring a computer tech
Just my 2 cents
Cheers!