Graphics card question

Hello and welcome to the forums
DDR2 vs DDR3 doesn't make a noticeable difference in gaming.But going from a Q9300 to an i7 CPU will give you a boost.
As for 480 vs 5970, well 5970 is faster and runs cooler and quieter but its costs more.

^+1

I am thinking to wait until fall that the new nvidia 485 will be released.For ati that is faster is common sense because it's 2 chips but with nvidia it's a new single chip.All these years i prefer nvidia because they are more reliable.I would like to hear your opinion about that, for the first time i am thinking to buy the 5970 card because i have read a lot of reviews.I don't know what to do!!

What resolution do you play at ?

Resolution: 1680x1050

For your resolution, HD5770 or HD5850 just more than enough for the average use...

True
There is no need for either GTX 480/HD 5970 for that resolution, a 5770/5850(in case you want to play with AA/AF) suffices

But for the upcoming games like crysis 2 and metro 2033 i will need the best card to play it with full graphics.I have an nforce 780i sli motherboard ,it would be better to prefer nvidia cards?

No one knows the system requirments of Crysis 2, but as for Metro you'll be fine(however the game isn't very well optimized)
As for your board,well a "Single" ATI card will work on your board.

When a 5770/5850 can handle every game fine on 1680x1050, why go with 480/5970 ? either 480 or 5970 will shine at high resolutions (FULL HD+) and won't show their full potential in lower resolutions.