well I live in Bosnia in my country.. one HD5870 costs 1000KM or converted into USD 700$ so 550VX is enough you say because one worker in computer shop (I dont belive him) said that this card needs 1000W power supply I throught that he is crasy I think he just is trying to steal cash from me
# PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard.
# 500 Watt Power Supply is required.
# 600 Watt Power Supply is recommended for CrossFireX™ System.
# 2 X 75Watt 6-pin PCI Express power connector is required.
# 4 X 75 Watt 6-pin PCI Express power connector is required for CrossFireX™ system.
Yes the guy at the computer shop either doesn't know what he's talking about, or does not have your best interest at heart. A system with a 5870 will use approximately 350 watts under maximum load, which would not be achieved through gaming alone, so a 550 watt PSU gives you plenty of headroom.