Hey, i just started playing mount and blade warband with eyefinity, and it is just so awesome to see those wide views of a cavalry line charging the enemy. So, totally worth it.
Also, although 3x 5:4 monitors has it's issues (with widescreen cutscenes being rendered poorly), I still think it's the best bang for buck (moneywise) that you can find. an entire 3 screen setup for 300 bucks (avg 100 bucks per monitor).