That will do but You won't like the experience though. Also you need a powerful graphics card to play games on two or three screen. You can use eyefinity to do normal stuff but you're gonna need a better gpu for gaming on a multi screen setup.
As already stated, it will work but every monitor's resolution will be set to the lowest resolution of any of the 3 single monitors which means that it will look really odd and out of place.
You could always try 3 19" monitors with the same resolution (don't have to be the same brand). That's what I did, I have 3 19" monitors, each with a resolution of 1440x900 giving me an Eyefinity resolution of 4380x900 (with bezel compensation) and it runs really well. I also have a 4th auxiliary screen for hardware monitoring during gaming.