I cannot speak for the 6870, but I bought a XFX Radeon HD 6850 from Amazon about 3 months ago for less than the prices you quote and am very pleased with it. It was a PCA recommended graphics card so you can't say fairer than that.
It works well at the full HD screen resolution of 1920x1080. I am not much of a games player, but it does all I need it to do. My only minor criticism is that the fan can get noisy if the graphics card has to work overly hard, but that rarely happens in my case.
Have a look here XFX graphics card