My soon to be bought system will contain 2 radeon 4770's along with an AMD 790x mobo, phenom II x3 720 as the more important parts. What kind of PSU will be needed to keep it all running safely? I've been looking at a corsair 550w psu, will that suffice?
The corsair should be plenty, one for its reliability, two, it meets the minimum required for the cards. The 4770s are great cards and baring any issues with crossfire scaling they even out perform at 4890 at times. Good buy
It might just be me but I can't find the 4770 in that list. According to that list a pair of 4890's can run on a 650 W (If I read it correctly that is) so I don't suppose I need anymore than that, but is it safe going down and grab a 550 W ? I'd hate risking anything in my rig
I've tried using this Corsair PSU calcualting tool but the 4770 are apparently too new to be included. A pair of 4850 along with my cpu of choice was able to run on a 550 W PSU but do those cards require the same amount of power?
In any case I'd like to be safe in case the PSU ages or I choose to overclock my CPU a little bit.
Unless you plan on heavily overclocking the entire system the Corsair CMPSU 550VX will be more than enough, it can, as you said, run a pair of HD4850 in Crossfire and they need rather more power.
Of course there's no harm in getting a more powerful unit, just stick to good quality brands and check prices, there's no point in paying a premium for for something you do n't need!
Best are: Pc Power and Cooling, Antec, Silverstone, OCZ and Corsair.