We have not gone this path but I can attest to the fact that just knowing my wife is attracted to black men and has a desire to sleep with a black man arouses me in ways I've never known. There is something different about my wife in the way she talks about black men, she describes them in ways she does not describe me, and the way she talks of their manhood, I can tell she has a greater respect for the sexual prowess it represents to her as a woman.
Having said that, my wife has a black "friend" she is interested in, however initially I want to be there and watch, it means a lot to me to find out for myself just how much she wants to be with a black man.