300 to 400 could actually be overkill for rust. I've known people to play on integrated graphics, albeit with lowered graphics.
You could get theMsi GeForce GTX 980ti OC but for 90$ more you could get the hybrid water/air cooled version from EVGA
but you could get the more popular evga OC acx 2 plus backplate. But overall the first card would fit you best with that price. It'll run hot, but beautifully. No problem with rust. Make sure you have the watts to support it though.
I personally have 2 Gigabyte G1 Gaming, but they're more out of your price range.
If you just want to play rust, you could get a cheaper card and save money