I have a HIS HD 5850 iCooler V (plain) and it is not very different from 5830 but way ahead of 57xx series cards. Just a suggestion.
I would recommend at least a 550W 80-series power supply. I personally find Antec 550W/650W or Corsair 650W power supplies best for gaming rigs. The reason why I say that is there is almost no price difference between 500W and 550W/650W power supplies when it comes to the extra room and cables you get.