5750,5770,5850,5870,5970 are all capable of powering 3 displays, the third display must connect through the DisplayPort via Display port or a Passive VGA or Active DVI converter

6750, 6770, 6850, 6870, 6870x2, 6950,6970, 6990 can all output up to 6 displays, the first two may be connected via dvi or hdmi but the third and forth displays must connect through the DisplayPort via Display port or a Passive VGA or Active DVI converter. 5 and 6 are only available when the display ports are daisy chained or split.

Crossfire - a note about crossfire, currently AMD drivers will only allow you to use the outputs of the primary card in a crossfired set. The 24-display 5870 eyefinity flight sim was a linux box designed to utilise the 24 outputs as a single array, it is beyond the average user’s capabilities.