Stay away from the 5830s! One of my 4890s died and I rmaed it with Asus explaining I run two in crossfire. The sent me an e-mail stating they had no 4890s to replace it with and would I accept a 5830 in its place, or I would have to wait for a 4890 to come in and be repaired and sent to me. I accepted the 5830 and reiterated I have had two 4890s in crossfire; would the 5830 work? They said no and told me to send the other 4890 in and they would send me another 5830. They run craptacular! The 4890s were faster than the 5830s in crossfire.
I would go with a 6950 and later crossfire it with another 6950 to double the frame rate...with these two cards it actually does double.
I would go with a Corsair, Thermaltake or Antec psu @ 750 watts. That way you can Crossfire in the future.
You found out the hard way to stay away from ECS products...just remember that lesson in the future.