NVIDIA and AMD are the chip set manufactures, they only make the chip sets, not the cards you buy online or in stores.
No you can buy GPU's manufactured by nvidia and AMD. I know someone who owns a 560 ti (I think that's what it is) and it's made entirely by nvidia.
Can you link me to it then?
He said "other than", not "better than". Try READING.
Is there any better brands of GPU's other than ASUS?
Sapphire
http://www.amazon.com/Nvidia-GeForce-GTX-GDDR5-Graphics/dp/B005O0G3FC/
Man Amazon has everything :O That's pretty cool. I understood that partners with AMD and NVIDIA got the reference models but I never knew they sold them like that xD Coodos.
I think Sapphire is the best brand if you're going for a low to medium-range card. They're cheaper than the others and are pretty reliable, I use a Radeon 6870 from Sapphire and it has run fine for the past year and a half.