Is this computer a custom built computer or a computer you purchased from a computer manufacturer? If it was from a computer manufacturer please provide make and model. From this info we can better assist you as for not every video card will fit in every computer. There may be spacial limitations on the size of the video card you can stuff into the box. If you have plenty of room and a PCI Express slot available, then it comes down to having the proper power supply to power the system with that performance video card.
Do you have a video card in mind?
Is there a list of games you will be playing at high graphics settings so we can make sure the card is a good match to your needs?
Do you have a preference of nVidia or ATI (AMD) video cards?
Do you have a fps requirement, if so how many fps are you looking for with the games in mind at high settings?
Lastly something to consider would be that if you go too powerful of a video card or too heavy of resource requirement games, there is the potential for the video card to be of greater performance than the Core i3 CPU in which the Core i3 would be a bottleneck for system performance, as well as the Core i3 can just struggle no matter what video card because the video game is very demanding of processing power. A Core i5 would be better, but thats not to say that this Core i3 wouldnt play the games you want to play etc. Knowing what games you have in mind we can determine if the Core i3 is going to struggle or be a significant bottleneck or not.
