Take a look at the charts section here for test results, you can google for the specs of the cards you are interested in. 50 cards requires going back 2 generations so much of the testing wouldnt be relevant.
Well the best spread of tests i know of is at techpowerup You can pick a card from the review section and you get a good spread of cards its compared to like this
http://www.techpowerup.com/reviews/Powercolor/HD_4890/