My pc is Asus m51ac-tr002. It has a weak screen card which is Nvidia GT640 and i want to ask, if i can change it to a gtx or not? I am afraid that size might be small or volt (power) might not be enough. If you used this pc and added a new GTX or etc please help me, i want to play next gen games on nice quality. And i would like a recommendation for a new Nvidia also.