@TJ99:
The HD7850 uses less power than the HD6870 !
I might have been thinking about the HD7870. or 7950. That's why I suggested the PSU calculator to get a more accurate result.
I actually have no idea about how the Huntkey PSU's perform as I've never used one. From what I've seen though they're at least not like those Fong Kong things that come with cheap cases and claim to be 600W yet weigh like 200 grams.
What I do know, however, is (1) that many people use PSU's that are rated MASSIVELY higher than their actual requirements and (2) they rarely, if ever get hot enough to become an actual issue especially in a decent case, (3) a PSU is most efficient at around 50% load, reducing below and above that (which is why the 80plus certification is measured at high and low loads) and (4) it spends most of its time closer to the bottom end (20% load or less), with only a small percentage of the time being at peak power draw.
Thus, all these people banging in 700W+ AWESUME EXXXTREME MAXXXX GAEMER PSU's to run a single midrange card setup, with a stock CPU are actually converting more energy into waste heat, since the PSU almost never actually operates at 50%. Largely irrelevant though as the amounts of energy wasted are relatively small, just saying if you really are that concerned about efficiency you shouldn't go too big either.
Not to mention the biggest issue, a good PSU is expensive and it's a big waste of money buying one if you don't need it. The easiest and cheapest solution is just to see if it does work with your current PSU, and if it doesn't,
then upgrade to a bigger/different one. And there's nothing wrong with using the Molex-to-PCIE connectors, that's why the cards come with them. I've been doing it for years.
Edit: Agree with the post above, some of those are good brands and what I would suggest you get as well.
IF your current one doesn't work.
.