8gb with 7700

Honestly, you could get away with it but you'd be wasting your money by not investing in more with a CPU and GPU like those. 8 vs 16gb is what, a $40 difference?

Not to mention, 8GB is not so much the gaming standard anymore. Most newer games will run smoothly with 8 until you up the processes running at a time, at least in my experience. I would strongly recommend 16GB for more modern gaming.
 


Monitor your usage and don't upgrade just to get a larger number with no value to you. 8gb is more than most need. In our house there are 3 avid gamers only one of them ever goes over 8gb.