AA = Anti Aliasing. It basically makes objects look crisper and makes lines that would otherwise be jagged, straighter.
AF = Anisotropic Filtering. When you're looking at an object (a panel) from an angle, the textures on that object pile up on eachother, making it look blurry/messed/ugly. Anisotropic Filtering makes textures that are viewed at an angle look as if they were being viewed face-on (which is the best).
The monitor size and response time are good, but a native of 1400x900 might not have been such a good idea. Ideal is 1280x1024 native resolution. If you're playing at anything other than the native resolution, you'll get performance loss from the monitor. It will probably affect response time for the worse as well
There are really no surround sound headphones. As in 5.1speaker headphones. Good ones will cost you a pretty penny. Instead, just go for some awesome 2-speaker headphones like Sennheisers or Icemat Siberia, I believe they're called.