One more thing to consider is screen resolution. Yes the millisecond response time is very important for see things as fast as possible. But if you want to game at 1920 X 1080 and your card is old and weak you wont get a descent frame rate in which to play.
First determine what your GPU can handle for resolution at playable frame rates. Then look for a monitor that has that resolution and has a 1-2 ms response time.