I have written a overview where i calculate most common GFX cards used for mining as of now CoinRamble.com - GRAPHICS CARD COMPARISON OVERVIEW i compare cards against each-other and some graphs to visualize it all.

e.g

http://coinramble.com/wp-content/uploads/2014/03/khs-per-kw.png


and a real world scenario:
http://coinramble.com/wp-content/uploads/2014/03/six-card.png