CPU clock speed and the memory bus on your video card are both important factors. If you're going with one of the quad core i5 CPUs the 760 would be better than the 750. As far as a graphics card is concerned, not all 1GB cards are created equally. I'd recommend either a GeForce GTX 465 or a GeForce GTX 460 with a 256 bit memory interface. If you prefer and/or can afford a GeForce GTX 470 or 480 then all the better.
A higher clocked CPU and a video card with a memory bus/interface of 256 bit or better. The amount of RAM you're concidering is right and with an i5 you're obviously rolling with DDR3 which is right. You need to keep the CPU speed and video memory bus/interface in mind. Also make sure you get a large enough PSU for your graphics card.