I host a Killing Floor 2 server, so I can't speak for the games you've listed above. However If your hosted server games are anything like mine in regards to performance, you'll likely not have to upgrade your cpu. I have a 2500k i5 processor and when I host my killing floor 2 server, my cpu is essentially idling. In my case server hosting doesn't take up barely any cpu resources as opposed to playing the actual game. What I would suggest is host your servers on that computer the way it is and monitor cpu utilization, then make an informed decision if more cpu allocation is truly necessary. You'll likely be pleasantly surprised to find out your computer will make a great game server just the way it is.