I looked into this setup but it gets pretty ridiculous if you want to do any gaming. You want 4k @ 60hz with 4:4:4 color sampling at a reasonable <40" but it soon begins to feel like you're hunting a rare animal. With only hints and whispers strewn throughout a dark abyss of forums threads and amazon reviews. The kind of places where people put AMD driver revisions in their signatures. I don't think we're quite there yet.
Can you get a 4k display and use it at its full resolution for everything but gaming, and then just switch to a lower resolution for gaming when you want the higher refresh rates?