I want to ask, i want to buy 5770 Crossfire... Can 5770 Crossfire beat 5870 single card in gaming experiance...?
They can, but it is really game dependent and settings dependent. Results from various tests show that the 5870 slightly beats the 5770's in max detail benchmarks. It seems that 4xAA and below the 5770's are equal or better but past 4xAA the 5870 pulls away by 5-10%. Crossfiring 5770's is cheaper but limits your upgrade path down the road. I personally am getting another 5770 for CFX.
Well, resolution matters. If you're going to be playing Crysis on at 1200x, than a 5870 is complete overkill. Anything 1920x (max details, AA, AF, etc) and over you'll want the 5870 most likely. If you can afford it, I'd go with the 5870. If you want a setup that will still get the job done and $100 cheaper, than the 2x5770's are better for you.
ooo.. ok, but in malaysia 5770 cost at RM700 so if i make it crossfire it will cost me RM 1400. And 5870 cost at RM1500. So in this case 5770 are little bit cheap then 5870 .
The problem if i buy 5770 to do crossfire i must change my PSU to 750PSU....
2x 5770's draw about 360w at max load in Crossfire. If your PSU is anywhere from 450-550w, and it's a major brand name, you should be okay. The rest of your system specs would help determine this though, as you don't want to take any chances.
Edit: I checked them out, what exact AMD processor do you have?
A 955 at full load seems to push about 300 watts at 3.2Ghz. I honestly would get at least a 650-700w PSU. 550w would most likely be too low, even for a Corsair. The 750w Corsair Hx is a great option. Amazing PSU built to last, I was thinking of nabbing one myself, for when I CrossFire.