By far a new gpu will give your more fps and the biggest boost to your system if you get the 3060ti.
Monitor first and then if youe not happy gpu, cpu motherboard and memorry will probably give you a max 20% performance inrease in gaming where a 3060ti is at least twice the performance of the rx 570.
Wow that is a huge increase.
I had the RX580 prior to the 3060ti so i'm assuming it was slightly better than the 570 ?