In the Toms Hardware article..Best Gaming cards for the Money" May" edition, the 6870 is listed as best card for $170..actually its tied with the Nvidia GTX560.
To get something better you have to jump up to the $220-250 range. Asus, XFX, MSI, EVGA, HIS are genarally good brands. Most companies will make a fairly stock card and then usually a couple of other higher performance models of that same model. That is why you may see maybe an EVGA card for a given price, then see another that may look alittle different, and cost a bit more that is also EVGA (or ASUS, MSI, etc)