I'm in the process of building a new machine, and I'm trying to figure out which brand of video cards is better for triple display(AMD or nVidia). I've read AMD's cards offer it. But does nVidias? Some of their cards have 2 DVI & 1 HDMI or Displayport. Could I use all three?
Most of the current AMD video cards support Eyefinity (triple display support). AMD has the advantage as you only need a single video adapter for three displays, NVIDIA's solution requires two identical (model-wise) video cards in SLI for three displays.
If you're going to go with AMD, one of the three monitors will require an active DisplayPort adapter, which can be found for around $30 USD.
Like Matt Haley said you may be able to get a GPU with support for 3 monitors in an AMD/ATI solution but not every card has this, refer to the box and specifications on the specific GPU for more info. NVIDA have taken a fairly solid stance of needing 2 cards, the major reason for this is that if you are going to use 3 LCD's for gaming you require SERIOUS GPU power and SLI is practically a must for most games.
Even if you are getting a single 3 output solution by AMD/ATI i would suggest you still invest in crossfire if you intend to use it for gaming.
if you do not need to game you may be able to get a low end card and add it to your system alongside your primary GPU, it wont provide SLI and any graphical applications open on that specific LCD will suffer but it would be useable for most things. I should note that this is old knowledge, cant tell you if this works anymore, do your research.