When I was a young lass, I married a man that I loved very much and I thought loved me in return. I knew he had a previous relationship with another woman and I was led to believe that was behind him. About 1 year into our "marriage", I started seeing a strange long distance phone number on our bill (there was no internet at the time) and decided to call it. I can't even begin to tell you how hurt and devistated I felt. He kept telling me they were "just friends", he "needed someone to talk to". I thought that's what he married me for. To be friend, wife, lover, etc..... Needless to say, he never was truely over her and our marriage ended a short time later.
My point to this story is that I've been on the other foot, as I'm sure many other here have been as well, and it hurts like Hell. I couldn't get over the betrayal of trust, amongst a host of other things, that a marriage is supposed to be built upon. Does you wife know how you feel about this other person? If she doesn't and she finds out, I'm fairly certain she won't be too happy about it. Or, maybe she does know and is ok with it? How much are you willing to risk?
Edit: Sorry, not trying to sound preachy, just thought you might like to hear a story from the other side. Good luck to you.