wasabi91 :
Should i ugrade my Athlon X2 5050e dual 2.6 processor to a Phenom x4 2.6ghz quad core and then overclock it to 3.0? I mostly would be using it for gaming (i dont want to buy a new mobo). But would i see a significant increase in games like oblivion and fallout and gta iv? ( i have a 5770 HD with 4gb ram)
The key word is significant. Your 5770 is already very good, so I suspect not.
To better assess your options run these two tests:
1) Run your games, but reduce the resolution and eye candy to a minimum. This will simulate what will happen if you upgrade to a stronger graphics card. If your FPS improves, it indicates that your cpu is capable of driving a stronger graphics card to higher levels of FPS.
2) Keeping your graphics resolution and settings the same, reduce your cpu power. Do this by removing the overclock, or by using windows power management to set a maximum cpu% of perhaps 70%. If your FPS drops significantly, it indicates that your current cpu is a limiting factor, and that a faster cpu would help.