To easily monitor real graphics lag, you should download FRAPS. The free version should be enough for this.
After installation you should be getting a digit in your top left corner.
Graphics lag will start to be noticeable really well at about 20FPS or lower, 20-30FPS is doable and above 30 is good. 60 is perfect ofcourse.
Seeing you have a good computer, this shouldn't be a problem.
As for network lag, the only thing you can do if your PC is fine is to get a better connection.
Though, you might want to search for other causes like a forgotten torrent, pando media booster, viruses or other people on your network that might use up a lot of bandwidth.





