I currently have a Core i7 920, 2xgtx260 sli'd and 2 500gb wd hd's on a Corsair 700 power supply.......im looking to update the video cards to 2xgtx470's.....will i need to upgrade the power supply also? or will the corsair be fine for the 470's?
You will want a 800W or higher, 850 preferred, to run those cards. You could get by with less but you'll be running your PSU very rough and it will most likely wear on you quicker.
Remember that the 470 needs two 6 pin connectors, so make sure the supply you purchase has those connections and also taht it is SLI ready. Most high end will be anyway, but be certain you're getting that.
I'd say a 700 watt might actually run em but you'd be pushing the psu past 700 watts under load (corwairs usually can go 15-20% over load) however i wouldn't reccomend running em on just the one as it'd wear your psu out fast. i'll echo going up to at least an 850 watt psu, with dual 470's and an i7 900 to be safe and still run in good efficiency/for the longevity of the psu , stick with corsair if you can, they are about as good as it gets