Question which should i choose?

[imaplantr]

Hello First of all here are my specs
CPU: i3-8350K
GPU: RX 570 4GB
RAM:16 GB Geil
Motherboard: Asrock H310M-HDV
PSU: EVGA 450 BT 80+

Okay so i have saved up some money to upgrade my gaming experience it's kind of lacking in ways so i'm Puzzled between a either
A GTX 1660 Ti
OR
A 144hz display "MSI Optix MAG24C"

and i need help deciding what to get

 

[butterfig]

You should upgrade to a 1660 Ti as an RX 570 would not perform well at 144hz, unless a lot of your settings are low. If you get a 1660 Ti you will be able to run games from med-high at a respectable FPS rate, as well as at buttery smooth 144hz. Hope this helps.