The only thing I don't like about those Mass Multiples monitor setups is the fact that they don't accept DVI connections, but rather use the older VGA connectors. It's no big deal but if I was going to drop a couple grand on monitors, I would want them to be a little more "future proof" since the industry is moving away from analog controllers and displays.
But for the sake of argument, let's say you did get those, so therefore you won't need a video card with DVI outputs. That means you'll need a multihead card with VGA outputs that can do at least 1280 x 1024. I don't even know if there is a "best" card to meet those qualifications because there are so many available that will do the job these days. Matrox, Appian, Nvidia, and ATI all have multi-port cards with vga outputs that will easily handle the graphics requirements of your trading applications. In fact, you could use a 4-year old card from Appian Graphics or Matrox, and they would still handle your graphics needs with no problems (assuming of course you aren't also using 3-D appliations like games, CAD, etc. on the same machine.)
In the past two years, multi-monitor video cards vith VGA outputs have become commodities so if I were you, I would simply look around the net for the best deal you can find in your favorite brand.