I want to upgrade my x51

hi, im new to the forum and i would like to upgrade my x51, but i would like some tips and green lights if it is possible.
My current specs are:
intel core i7 3770 3.4ghz, with an nvidia gt 640 and 8gb memory ram. but i have some problems running some games in ultra settings. so i wanted to upgrade the psu to a 330 watts, a nvidia gtx 660 ti graphic card and i want to know if it is possible to upgrade the memory ram to 2x 8gb 1600MHz (16gb total) of memory ram and would the motherboard handle everything fine?
I just bought an evga gtx 670 FTW edition finally upgrading from a gt 640 sure will be really noticible and i think i would be good for some time, it will be my first time upgrading a computer. Hopefully good news come soon for another great graphic card compatible with our belove x51