I have this card (HD5850 Toxic 2GB), I run 'Arma 2' on it and it runs very well. The fps can vary from 110+ down to 25+ depends on island (map) your playing and clutter, city or open area (also V-sync disabled, ingame). Overall the card is great, would recommend it to anyone wanting a card to handle heavy games, like 'Arma 2'.
Rgds
Chris