Sorry, you can't play gta5 at 60fps in 1080p with your pc ( P5G41T-M LX ). Here is review for gta5. https://www.techspot.com/review/991-gta-5-pc-benchmarks/
But if you got the C2Q and play the game in 720p, you may get 60fps. And it depends on what budget you get for the which C2Q and GPU.