This is going to start an argument.
I have to point out that despite what you may have heard a 120Hz (not MHz) monitor is not really a good choice unless you just need that (3D or whatever). The problem is that if you are one of the lucky people that can distinguish between 60Hz and 120Hz refresh rates (everyone I know can with just a small amount of exposure to the difference) then you will not like the result. You are better off going for a larger monitor, or at least up to a point. I tried everything up to 32" monitors and finally settled on three 24" monitors. Your system can handle this easily and all you need are the monitors and the cables.
A couple of things to be aware of are that the larger the monitor becomes the easier it is to distinguish individual pixels. Since you have nearly 2,000 horizontally on each monitor it will not be much of a problem until you get a very large monitor. What does affect your view though is the span. If you intend to use three monitors then you need to think about peripheral extents. To some degree you can overcome view limitations by pushing the distance, but then you start to regret doing that when you are scanning for dots on the deck and other scenarios.
Smooth frame rates are more important than large numbers of frames, so don't be afraid to use vsync. Stick to the native vertical resolution whether you span three monitors in surround vision or not.
If you do go with three monitors get three of the same monitor. There are methods of using varying resolutions even, but they are not ideal solutions for Aces High especially.