What is the best graphics card for £200/$310?

I am currently under the process of building a computer and I am facing a difficulty as to which graphics card would be the best for my money! Please help. I am preferably looking for an Nvidia core, however of course I will look elsewhere if it would benefit my system. Any help is much appreciated! Thank you very much!

For around 200 a r9 290 would probably give you the best performance.

A 970 from Nvidia would be slightly stronger and consume less power, but that would be quite a bit over your budged. 

You could probably get a 770/680 for around 200, but those are noticeably weaker than a r9 290 and have only 2gb vram instead of 4gb.