CX500, what's the best card i can get?

[TwgNozzy]

Specs:
AMD FX 4300 Black Edit, Clocked to 4.4 Ghz
MSI GTX 660 (no Twinfrozer)
Corsair H70
Corsair Air540
Corsair CX 500w
Crucial 120Gb SSD
500GB seagate(?)
4 aditional 120mm fans
Asus m5A97 R2.0
8Gb Kingston DDR3 ( 2x4Gb)

I want to uppgrade my GPU but i have no clue on what's best to buy when it comes to limitations of my PSU. what i am looking for is what Recomended.
i'm thinking of a GTX 780(maybe TI?), or a good AMD card (R9 290x?)

note: i don't think i will overclock the GPU.

i just want the best GPU i can get, not important which brand or Manufacturer.

thanks in advance

 

[spentshells]

Well the best card would be the gtx970 at this time. The 780 and 780 ti draw a lot of power.

 

[TwgNozzy]

but what about AMD cards?

 

[spentshells]

280x

 

[TwgNozzy]

280x

Thank you very mutch :3