Simple answer is no - there isn't a 4K monitor that can do 250Hz. Closest you're going to get is this:
ROG Swift PG43UQ is the world’s first 43-inch gaming monitor with display screen compression (DSC) technology that delivers native 4K visuals at up to 144Hz via a DisplayPort 1.4 cable.
www.asus.com
As for a matching graphics card, most games won't run at 250 fps at 4K, but stand any fighting chance of getting anywhere near that you'll need two
GeForce 2080 Tis in SLI - one will only get you just get you half way, and even then, only in a small number of graphically light titles.
Graphics cards don't drive loads through the CPU - it's the other way round. But if you're wanting to play games at 4K at the highest possible frame rates, then you'll need either an
AMD Ryzen 9 3950X or an
Intel Core i9-9900KS.
Lastly, you'll need to sell one of your kidneys to buy all of this.