[Mashiro]

So you're looking for a cheap entry class 4K video editing GPU for your system? The GTX 1050Ti indeed seems to be a hot topic in this terms and indeed a RX 580 is a great alternative. Considering you have a good CPU (3600 should do very well) and a lot of RAM... don't forget to actually get the proper storage type for 4K editing. A HDD might actually be too slow for a smooth timeline scrolling when editing.

I'm curious what kind of software you want to use for editing though. And to dail in better, what's the exact budget for the GPU? You mentioned March 2020. In that case I'd wait longer until I would make a decision. Prices might drop and you might be able to afford even better cards for the same budget.