@Setanta,
I will tell you from one person to another, do not cheat. It is absolutely the worst thing you could possibly do. I am speaking from the seat of someone who is currently in an affair, emotionally attached, and cannot find the nerve to leave either woman. Trust me it is painful, it will destroy you emotionally, and not to mention the consequences are huge and could not only cost you your relationship but your life. If you want someone else first leave the person your with then move on. You cannot have your cake and eat it too. Trust me this hardly if ever works out for the best. Of course we all think we are that one in a million, but we are not.
Good luck..