The i5-4440 combo is ideal for right now.
The i5-4670K may be better in the future when you upgrade the graphics.
My advice is get the i5-4440, especially since by the time you upgrade your graphics we will be starting to switch to DX12/Manlte/OpenGL that is better able to use your CPU thus possibly eliminating any bottlenecks there.
For example, most games can't use more than 50% of a 4-core CPU's resources due to the game software. Once that limitation is overcome your CPU is 2x more powerful in terms of what the game can actually use.
(BTW, if you see all four cores being used in the Task Manager that doesn't mean the game is fully threaded. A game might only be able to address TWO cores but with hundreds of small processes...