I agree (and so does Kate) that married men are better. My wife loves to be the 'fun fuck' for longtime married friends of ours. It turns Kate on to be a fuck-toy for the husbands of women she knows. Going out to dinner on Saturday night with a couple, when the husband was at our house Friday night fucking my wife is hot.
A few years ago we were working with a married Realtor couple on some property. The husband stopped by our hose to drop off some paperwork during the day when he knew I was at work. He really just wanted to find out if he could fuck Kate. Of course, my wife was happy to take him to our bedroom and show him a really good time.
We worked with that couple for about six months and the husband fucked my wife several times. He thought that I did not know, and his wife certainly did not know. Having meetings with them was much more interesting after he started fucking my wife.