Comes down to what ports you have available on your motherboard, and what size power unit you have. That will narrow your search greatly. If you have a 250W PSU, and you buy a 1000W card, you'll hurt the motherboard.
What research have you done, what choices have you narrowed your search down to?
I trust nVidia over other brands, just by years of listening to people and that is all I've ran and have good rates, no problems, they keep the drivers up to date nicely too automatically.
So, let us know what is available on your mobo (ports), and what size PSU you have, and we can go from there