I've used my own "Eyefinity" setup to game across 3 monitors and in the end it wasn't worth the investment. You need a large desk and ideally a triple-monitor stand too. A decent graphics card is a must. I ended up spending over $1000 altogether on mine and that doesn't include the cost of my computer. It doesn't make the games any more fun.
My advice? Get a single, nice monitor. You can avoid all the hassles, costs, and limitations of a triple-monitor-gaming setup.