Thank you guys for explaining what g-sync is and how it relates to the monitor.
I do not plan on OC'ing my computer as I think that's really just beyond my scope. I also did go ahead and purchase the tower/case linked in the first build as it was aesthetically pleasing and seemed to have a lot of space to put the parts in.
As far as I know, can't you just buy Windows 7 and then get the free upgrade to 10 from that? I get pop-ups like every day on my computer wanting me to upgrade from my Windows 7 Vista Home Edition to Win10 and I never do it. And you're totally right about my AMD card lasting a long time. My current card is an amd Radeon 6800 series and it came out in 2010. My CPU is an Intel i5-2310 2.9 GHz. It's worked great so far but with the graphics updates in Legion and computer already being so old, I felt it incumbent upon me to build a new one.
I'm a bit nervous about splurging on an i7 if I'm not going to get the most use out of it, barring overclocking which I do not want to delve into.