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!

Unless you need CUDA for professional work then there is absolutely no reason to want Nvidia over AMD, favoring any hardware company over another is a pretty bad idea, just go with what performs, is stable and is cost effective.

Depending on how much you're willing to stretch that amount I've seen a few r9 290's around that price on amazon. If you really cant spend more, or aren't willing to save for longer you could get a 280x although the 290 is far superior.

http://www.amazon.co.uk/XFX-Radeon-Edition-Graphics-GDDR5/dp/B00HHIPM5Q/ref=sr_1_3?ie=UTF8&qid=1419796081&sr=8-3 here's an XFX one for just under £230

http://www.amazon.co.uk/Sapphire-TRI-X-Graphics-Card-PCI-E/dp/B00HFA44YQ/ref=sr_1_10?ie=UTF8&qid=1419796528&sr=8-10 and a Sapphire TRI-X one for about the same,from what I hear sapphire is one of the best manufacturers of AMD cards out there.

http://www.amazon.co.uk/SAPPHIRE-AMD-Graphics-Card-DDR5/dp/B00IRTXPBM/ref=sr_1_3?ie=UTF8&qid=1419796717&sr=8-3&keywords=280x Sapphire Dual X 280x a nice card but the 290 is a better card.