i3 has 2 physical cores and 2 virtual named hyper-threading, i5 has 4 physical cores, i7 has 4 physical cores and 4 virtual. Some i5 can be dual core too. This is a short and poor explanation but it is easy to understand.
Windows 8/8.1 and Windows Server 2012/2012 R2
Microsoft's official Windows 8.1 Support Lifecycle Policy treats Windows 8.1 as if it were a service pack for Windows 8. That means the lifecycle calculations start when Windows 8 shipped, in 2012.
Support for the original release of Windows 8...
i would wait even for a rx 460 too and that mobo is too expensive to be honest, but i think you want to overclock that i3 :) because asrock have some sweet mobos for that i3 :)
Guys it might be worth to do a full scan with a fully 30 day activated malwarebytes antimalware pro software and give it a go, even a registry clean with ccleaner, hope it helps in some way.