I know it is a new/budget brand, but I've now purchased 3 different TCL 43S405's (work, home, wife's work). It is a 43" 4k monitor, with low lag, low motion blur and 60hz refresh rate. I've been extremely happy with them (once you turn on game mode and turn off HDR). $350 before black friday, they're $300 at Target right now.

Also, if you want a fantastic site to compare tvs/monitors apples to apples, you can't beat rtings.com. They grade every device on the same rubric so it is easy to compare and contrast. You can even tell it which qualities you care about most (or what use case) and they rate them accordingly.

http://www.rtings.com/tv/reviews/tcl/s-series-4k-2017-s405