May,
I realize everyone's different, but I just can't understand why, if you like Jane and Susie and want to socialize with both of them, socializing with both of them TOGETHER is a problem. If all three couples get along, why not get a table for 6? My first thought, if I were Jane or Susie, is that you or your husband disliked one of us or our husbands, and the 'just 2 couples' or 'just the 2 of us' is a deliberate attempt to avoid socializing with the disliked person. I think Jane and Susie have very much gotten your message, and they're sending the message back that neither of them is going to be a partner to cutting the other one out. Unless you're planning on an activity that one of them dislikes or can't participate in, I don't see any way to say, 'Just you, Jane, let's not include Susie' without hurting feelings. Even so, I'd say, 'Jane and Susie, how about a trip to the opera? Oh, yes, Susie, I know your husband hates opera...just didn't want you to be left out of the invitation.' I personally would feel VERY uncomfortable (if I were Jane) to have you say, 'Let's the two of us go somewhere, and not invite Susie.'