My PC consists of a GTX 980 Ti, i5 6600, gigabyte Aorus Gaming K5 motherboard and 16 GB of ram. I have a good case, ssd, loads of storage and I am wondering what should I upgrade and what should I upgrade to, I have a few options but please recommend some alternatives. Note that I can only upgrade ONE thing. So, the options go as, GTX 980 Ti to GTX 980 Ti SLI, i5 6600 to i7 7700K.I NEED AN ANSWER QUICK THE MONTHLY PAY JUST CAME IN I NEED THIS DECISION TO HAPPEN QUICK!