i only have a 60-80 dollars budget i research some gpu i found Radeon Hd 6570 and Geforce Gt 630 the two of them both have 2gb gddr3 which is better?
For $60-80 you wont get anything good. Trust me save your money and at least by a $150-200 GPU. Personally I'm getting AMD's R9 290 which absolutely kills for $400. It's got a clock of 662MHz-947MHz with 4GBs of VRAM and a memory clock of 5GHz GDDR5. I gaurantee you that you will not get a good GPU for $80. http://www.youtube.com/watch?v=sph6cjJeRdI
Please don't by a 6570 or 630, maybe a GeForce GTX 650 Ti Boost or up to a Radeon R9 270X. These are more worthwhile cards and deliver much greater performance.