darkspartenwarrior :
So I can have 2 different monitors and drag my mouse across/spread my desktop across, but for 3 or more they have to be the same?
You don't want to have two screens as one big desktop.
What you want is a MAIN screen, then an EXTENDED screen (but yes, your cursor will go from screen to screen). So on the main screen you'll see your normal desktop. When you launch a game it will simply run in the main screen and you can have a web browser or whatever you wish on the second screen.
Let's say you want to play a game with a website open:
1. Open your BROWSER
2. Drag to the Extended Monitor
3. Start the game
If you want more information on gaming, then you can read about Eyefinity:
http://www.amd.com/us/products/technologies/amd-eyefinity-technology/how-to/Pages/faqs.aspx
*You may find it better to disable the Extended screen while gaming if you don't require it but I don't have much experience with using two screens but I think I have the basics right. I did play around with adding my HDTV as a second screen and tried both with an HD5870, then a GTX680:
Screen#1 - 2560x1440
Screen#2 - 1360x768 (my HDTV via the PC-input)