The port in the back is for bass. The port should be away, no doubt, so that the bass does not become boomy. I also use a speaker that does not have a pass port in the back. But you have to realize that the speakers do have tweeters and mid-range sounds coming from the drivers. They first hit the side walls and the wall behind you and then reach the front wall - from where they are again reflected back to you. My belief is that the more time it takes for these reflections to bounce off the front wall (wall behind the speakers) and then come to you, gives you more perception of depth. By "treating" the front wall, you are killing off some of them. But you do not want to kill all of them and have a dead sound. Hence some folks have reflectors/diffusers instead of absorbers on the front wall.
This is in layman's terms. Someone more technical might be able to provide a better explanation.