Hi Winterfire, I found your post interesting.
My situation is different, but found some similaries.
My wife has a (man) friend, and we are trying to find a way to incorporate him into our lives long-term. But with the inclusion of him, I find myself wanting some side-company of my own. Not that I don't like his company, but he is a he, and we are both straight.
My wife finds it frustrating that I desire this, even though she listens to me and hears me out.
We also don't want to simply date different people, but finding the right person/couple to satisfy the needs of both of you obviously sometimes just doesn't happen.
It sounds like you two are at least airing your feelings/frustrations/emotions, which is critical to the health of your relationship.
Hang in there, and hopefully with continued communication you both can find fulfilling, satisfying relationships, whether with only each other, one additional person, or whatever combination you end up with.