OC is not necessary, but I recommend you buy OC-able components. Having overclockable components, even if not overclocked from day one, will help prolong the useful life of your system. For instance, people who own i5-2500s and i5-2500ks. The people with i5-2500s have had to upgrade already, whereas those who own i5-2500ks are still rocking because they are able to overclock and get performance equal to more modern CPUs.
Go for the MSI 970 Armor O.C. No reason to pay extra. Its all the same GPU.
Yea, the community is fantastic aside from a few rotten trolls. I came to this forum seeking help, and was treated really well, so I stuck around, hope you do the same!