I'm able to sit at a pretty comfortable 4.2 GHz. It's a decent cooler, but I highly recommend getting some different CPU thermal compound to use with it.
Nice build! I recommend buying the Battle Pass for DotA if you haven't already. You get a ton of cool skins for pretty cheap, and challenges always add some more fun to the game.
although 21:9 has been around for some time, some game, from VALVE specifically still doesn't support this ratio very well
Valve is still behind on some key things like this. If your Valve game of choice is DotA 2, then I would simply Google a solution. I saw a while back on r/dota2 about a 21:9 fix for the game.
In an NCIX video, they said that Battlefront was using around 7 GB of RAM on the highest settings, so 16 GB is not the worst idea in the world, especially with DDR3 RAM being so cheap right now.
Possibly unpopular opinion:
I actually like Windows 8.1. It isn't as great as 7, but I have it on my laptop and once you get used to some of the weird UI stuff, it's not that bad. Honestly, 10 was ruined for me by driver issues.
I went from 7 to 10, and I ended up having to go back to 7 because the sound drivers for my motherboard and for my USB headphones both stopped working one day. It was extremely frustrating because there was no way to actually press any update or uninstall buttons. You could click them, but nothing happened. So after at least 5 hours of puzzling with looking up solutions and reinstalling drivers, I gave up. So, be careful when updating from 7. I think a clean install of the OS will probably be your safest bet.
The cooler is nice if you want something a little more powerful and quieter than the stock cooler. It was a pain to mount, but it is pretty nice looking and keeps me at a solid 4.2 OC.
I would look into getting an aftermarket fan for your CPU so you can play around with overclocking. The 6300 is a great overclocker (most AMD chips are).
Thanks for letting me know about the FAF community. I have been a fan of the original Supreme Commander for years and I got the FA expansion in a humble bundle about a year ago. I haven't really thought about the game recently, but now I have got to play it again with this mod.