Get a 1gb GTX 460 and add another later if budget is an issue - would be my advice.
what psu would i need if i put if i use the 5800 6800 and over the 460 series , i mean to change the card in the future
thanks guys i will go with this build
this video says that 2 460 are better than 480
http://www.youtube.com/watch?v=PU9fbVejuew