GPU upgrade from 600ti

[ToniMarino]

Hi guys, I'm looking to upgrade my gpu. Its currently a Gigabyte 660ti.
Its hard to talk budget because the prices are usually higher here in Brazil. I was looking for something around R$1500, R$2000.
That's the price of a cheap 780 or 770, deppending on the seller.

My current rig is:
i5-4670k
Ga-z97m-d3h micro ATX
750w power supply
8gb Kingston fury DDR3
1tb HDD
120GB SSD
Gigabyte 660ti

What GPU would you recommend? Maybe some AMD one?
Thanks in advance!

 

[ToniMarino]

I'll mainly use it for gamming.

Titles like Metro Redux, Rome II total war, Battlefield, all kinds of game actually. I run a 1080p 144hz monitor and my gpu is struggling to run games at that resolution, that's why I want to upgrade.
Sorry, forgot to mention that.