The advice in 3.2 was a GPU with a minimum of 4gb of memory was highly recommended so that's where i'd go next, but don't expect it to suddenly give you a lot more FPS - remember even with OCS in now, the game has still yet to be optimized so $$$ on gear now may not result in actual improvements yet.
With that said, with the overstock of GPU's following the Mining decline, this could be the year to pick up a total bargain - there are still 1070's out there but 1080's seem to be selling out even before the sales.
To be frank, i'm surprised and delighted you are getting 45-60fps off a 2gb graphics card. I've got a 4gb RX570 which is just about between a 960 and 1060 and i'm getting between 25 and 60 depending on where I am in the 'verse so there is a lot of work for them still to do. When i'm playing my graphics card's RAM is maxed out so if I could i'd look for an 8gb to see me safely through Alpha. They will lower the amount of video card memory the game uses when they optimize but until that point it might just make a difference...?
