I extended my PC with two old monitors I got from my sister/brother-in-law. An HP1955 and an HP2035, with resolutions up to 1280×1024 and 1600×1200 respectively. Since my main screen is FullHD (1920 x 1080), Eyefinity on the RadeOn 7970 will set the height of all to 1024 when you put them in a group. Giving me a total resolution of 3840×1024. Not the best the card can do, but the best in this setup.
To save me the trouble of constantly setting up the group and gaming, and then switching back to a normal extended desktop (with max resolutions on each monitor), I created two presets in the Catalyst Control center. Easy. Just do your setup, go to Presets (second item in the accordion) and click on Add Preset. Name the preset so you can recognize it. Do another setup and add it too. Now you can switch between the presets by right-clicking on the system tray icon of the Catalyst Control Center and selecting “Invoke preset”. Choose the appropriate preset, and you’re done.