The cheapest route is to go single card and make use of the onboard graphics.All you need to do is run a mobo with onboard graphics with a dual output video card. Plug two monitors into the video card, and two into the onboard graphics. Then, go into the BIOS and set onboard graphics as the primary. This will leave them enabled, even with a dedicated video card installed. When you boot up Windows, it will then detect the video card, and let you install the driver for it. Make sure you install just the video driver, not the whole control center. If you do it this way, I recommend using an AMD chipset with an AMD video card to prevent driver issues. You also have to use Windows 7 or XP, NOT VISTA. Vista only allows a single graphics driver to be installed, which will limit your video card choices. I can confirm that it does work on 780G and 790GX chipsets.
If you go the multiple video card route, you do not need SLI or crossfire compatibility. SLI and crossfire combine the two cards' power for a single output. What you are doing is simply multiple cards. It will work on any motherboard with two PCI express slots. The cards don't even have to be the same, though I recommend that they are to prevent potential driver conflicts.
You could also use an eyefinity compatible card. Most only support three monitors, though there are a couple of exceptions, namely the 5870 eyefinity 6
(6 monitors) and the 5770 eyefinity 5
(5 monitors). You do not have to span the screens, they can also be used as individual monitors. Note that when going this route, two of your monitors have to be displayport enabled. This means that they will either have to have a native displayport, or you will have to use an active adapter
to convert the signal. You will also have to use Vista or Windows 7, as there is no XP support.
All that being said, may I ask why you want four monitors? I have found three to be a much better number. It's easier to manage, it looks better, and it's much easier to keep organized. It's also amazing for gaming, because the two extra screens simulate peripheral vision.
Originally Posted by nbrikha
If it's for gaming I'd move to AMD. A lot cheaper than Intel and you get better frame rates in some cases. Generally, bang for buck award goes to AMD. Asus M4A79T deluxe
<--This mobo will handle your GPUs better and throwing in this CPU will get you some fine tuned horsepower -->AMD Phenom X6
. I can't see why you'd need more than 16 GB of good RAM, 24 is a bit over kill.
I am using that mobo right now with three video cards. I've used four before so I could have eight monitors(random experiment). Works perfectly. My only complaint is that it's not a great overclocker, but with AMD that hardly matters since multipliers are usually unlocked.