GIANTS Software - Forum

Going to be upgrading my GPU this month and was wondering what's the best GPU to be buying as in either NVIDIA or AMD etc?

Do I stick with 4GB or go with 6 or 8GB?

From what I've read about AMD, is that their cards run hotter and consume more power.

Upgrading your GPU automatically means 8GB VRAM or more. At least if the RX580 listet in your signature is the one you actually have right now.
You basically only have a very few choices: AMD Vega 56 or Vega 64, or Nvidia GTX 1070(Ti) or GTX 1080(Ti). Anything else would be a downgrade or just at the same level.
Performance wise the Vega 56 is roughly the same level as a GTX 1070 and the Vega 64 at the same level of a GTX 1070Ti or GTX 1080.
The choice is yours. Just keep in mind: even though your CPU isn't that bad, it might be pointless to pair it with a high end GPU like a GTX 1080Ti due to it becoming a bottleneck.