for occasional gaming (on Mid/Low) my specs: cpu Intel i3 2100 3.10gHZ,mobo Gigabyte Z68M-D2H, RAM Kingstong Hyperx Blu 8 gb 1333Mhz,monitor Asus VH238 LED 23",PSU Thermaltake TR2 500W , Ihave seen on Amazon a EVGA GT640 110$ and a Asus HD 7750 110$, Both PciE 3.0 i dont know which one is better but my mobo is PciE 2.0 ..Bottleneck??
You will be fine, with low end to mid range cards, your CPU will not be bottlenecked. Also PCI-E generations are all compatible with each other, so a PCI-E 3.0 card will work on a PCI-E 2.0, 1.0 slot and such.
If you cannot go above $100, this card is stronger than both those GPUs too.
thanks.. i have checked your suggestions but i just buy from amazon, because newegg don't take my credit card , maybe i could add 35$ more to the budget and buy a HD 7770 135$ looks pretty good and its 120$ after rebate.