Best GPU for Gaming at $800 / £500?

I'm going to be building a PC, and I have quite a big GPU budget. I'm willing to spend $800 / £500 on a GPU.

Thanks!

MSI GeForce GTX 780 Twin Frozr OC £418 http://bit.ly/1aEPTX3

Gigabyte GeForce GTX 780 OC?

http://www.aria.co.uk/Products/Components/Graphics+Cards/NVIDIA+GeForce/GeForce+GTX+780/Gigabyte+GeForce+GTX+780+OC+3GB+GDDR5+Graphics+Card+%2B+3+FREE+GAMES+?productId=57506&source=skinflint

Are you prepared to wait? If not, the 780 is the best all-round, and highest preforming single GPU.

The 780ti and R9 290x cards will be released in the coming weeks.

"Nvidia's counter-punch, the GTX 780 Ti, will hit the streets on November 7 and will cost $700" 

http://www.pcgamer.com/2013/10/29/gtx-780-and-770-get-price-drop-in-wake-of-amd-290x-release-780-ti-gets-release-date/

Probably not sub £500 for the 780ti, but it might reduce prices of other cards.

I would reccomend the r9 290x.  However, if you're going to wait there will be models with non reference coolers.  This would give you a little extra money, which you could invest in other parts, or save up and buy another for crossfire!  The reason I'm suggesting this is because this card will most likely be on par with a 780 ti (After overclocking it might even be better).  Plus, with mantle and the 2 next gen consoles having and apu's there will be a lot more amd optimization and attention to drivers, etc.  So I really recommend this one over the nvidias.  You migt also look at the 7990s.  These cards and the gtx690 trade blows for most powerful card on market, the only thing is that they're essentially 2 cards in one, so you don't always get the best performance due to drivers, games that aren't entirely optimized, etc.

780ti.