Cpt Underpants :
Reading this thread has been very educational. I believe SNA3 has given a great recommendation and outstanding technical support to his conclusion. I especially liked the debunking of "recommended specs" and the folly of going completely off them.
However, I wholeheartedly agree with Mouse that the QUALITY of psu manufacturer can be more important than its sticker wattage, and in fact this is the case most of the time. consistent, clean power from a quality psu that will not degrade too far from its purported specs can be better even if at slightly lower wattage. ie. an XFX or Seasonic 550W would unquestionably be suitable for your 770. The question is not so much whether 550w is enough (as has been shown with fancy charts and such) but if Aerocool can deliver.
Hi - actually not a debunking per se, most of us know that Nvidia and AMD overstate the PSU
wattage required for their cards. They do it to allow for PSU's that don't deliver their rated specs,
and older PSU designs that don't allocate enough of their total to the +12v rail(s).
This is why realhardtechx and others that study this very thing are better sources.
Both of those situations are at play here, a tier 4 PSU that:
Tier 4 - Not Recommend for stressful situations. May not be able to put out full rated power above room temperature, and may slightly fail to meet ATX specs.
And only 35a on the +12v rail. Most quality modern 550w PSU's have between
40 & 45 +12vamps.
Right from Toms Hardware - figure the +12v amps needed for the GPU, in
this case 19, add 15a for the rest of the system, and add 5a safety margin.
That's 4a more than the OP has with a PSU that isn't likely to deliver the 35a
in any event.
http://www.tomshardware.com/forum/314712-28-please-read-determine-power-required
And, of course the OP has 'k' processor, so it's highly likely he intends to OC,
which itself will require more +12v amps.