I've got two monitors and thats me out of space. Big problem with Eyefinity is you need several identical monitors to do it well and the rig to mount the monitors properly. It looks awful with different size monitors and some things just won't work without identical resolutions on each. You can have four monitors just as individual screens like a normal multimonitor setup. The advantage of eyefinity is a single virtual screen space for tricking applications that dont support multiple monitors namely games to run.
But that doesn't work as well on even number of monitors as you need one to act as a center for most things like game and two for peripheral left and right with the fourth being the up direction peripheral. To get four to work 2x2 and use it for game you would probably have to strip the monitors down to just the panels and connections and mount them in a custom housing with a minimal gap between panels.
 - Good Eyefinity game config  - Not ideal just use normal multi monitors
Also you do need a huge amount of juice in the graphics cards to run at that resolution unless you drop some graphical options.
In terms of what you need the cards themselves will determine how its done different brands of cards will have different ports. The number of ports on the cards vary by manufacturer. You need to read the manufacturer manual and the ATI support stuff for exact details. ATI will have most of the documentation on Eyefinity so that should be the first port of call and worth giving the site and forums a good rake because useful info isn't always presented obviously for some of the less used features.
Best Eyefinity combo is three monitors one center and one left and one right. As a configuration it is also better as the peripherals don't have to match the center other than in resolution for it to look good.
Big eyefinity set ups are still pretty rare. Not every game supports such large horizontal resolutions without a lot of modding. Cost wise its prohibitive as for most people one good monitor is a better investment and laying out the £1000s for multiple screens just for playing games isn't practical. Not to mention you need a massive desk or custom mount to do it or a big living room as eyefinity actually works best with TVs believe it or not its cheaper to get three LCD TV.
Edited by warriorscot, 21 April 2011 - 11:10 AM.