Best card is the 7850 in that price range. However, looking at the specs, the 4890 looks like a nice card still. 256bit, GDDR5. Only thing I can see is no DX11 or OpenGL 4. Your choice.
The performance the 4890 gives me isn't the greatest at 1080p. I have to put graphics options to medium to get satisfactory performance in some games, but it looks horrible when in those settings, which is why I feel its time to upgrade, I bought it in 2009