Future proofing is probably not the best idea. It's better to get something a little weaker now and replace it in 2 years than get something that can keep up with high-midrange in 2 years and avoid replacing it. The 780 will probably be equivalent to something a third the price in a couple of years.
Additionally, having 4GB of VRAM isn't going to affect Dolphin, as AFAIK no-one has ever reported it using more than 1GB. What matters most is memory bandwidth IIRC. I don't think it's a 1-1 mapping, but getting a card with more memory bandwidth will definitely make dolphin be able to render at a higher resolution at fullspeed.
Additionally, having 4GB of VRAM isn't going to affect Dolphin, as AFAIK no-one has ever reported it using more than 1GB. What matters most is memory bandwidth IIRC. I don't think it's a 1-1 mapping, but getting a card with more memory bandwidth will definitely make dolphin be able to render at a higher resolution at fullspeed.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56