Thanks for the input. As for a strong marriage, I would feel very comfortable saying that about what we have.
The enough love for others is something I've always felt, though I'm not a fan of terms such as "primary" or "secondary", opting to use more conventional terms such as wife and girlfriend in this scenario. I've never been able to wrap my head around the idea of there only being one for each person. Those are some incredibly crappy odds of finding that "one" in a world of nearly seven billion people. Ha ha! When I was younger (34 currently, met at 18), it had never really crossed my mind. The norm for the world around me was just kind of falling in to place.
Wife grew up in a sexually repressed home and eventually, things just kind of came to the surface, which is what sent us down this path. Literally spoke about it for about two years before even doing anything.
The sexual compatibility could prove to be an interesting venture. My one concern there is my wife. We are pretty much a 10/10 in every aspect of our relationship as far as how we match up (direct match or complimentary...to a freaky level). But, the sex is usually "only" about an 8/10 and she focuses on that too much IMO. I love sex with her and all of the intimacy that comes with it. LOVE IT! We just aren't quite on the same wave length. But seriously...what better thing to "have" to work on? lol Sexually with the newcomer, it appears like it could be a dead ringer for me. And I fear this may upset my wife, though she has no need to be. A big chunk of the chemistry I feel comes from the D/s interest which there isn't a true interest in between my wife and I. She's not a sub which pulls me away from the true Dom aspects. I have a very Dominant nature in general. The thing is, my kink (if you will) is basically being a part of someone else's kink. So I can REALLY pour myself in to something like this if my partner is a true sub. But only if the recipient is seriously in to it.
Other than that, communication is extremely open between us. All three of us so far, actually. The direct conversation for this path has yet to come up since it's just not a good time yet. But I feel it may eventually and has been lightly discussed, almost in passing. And I'm just hoping to be as prepared as possible.
Oh...one other aspect that I think plays a very interesting role in this. As stated, she's going through a separation that I feel will end in divorce (hence, needing to stay back for now). But I'm not sure if this helps or hinders the situation and how it may affect her decision. To me, something of this nature is not be entered in to lightly. The issue is, every important relationship/marriage to her has failed. Parents, her marriage, both grandparents, all siblings but one, etc, etc, etc. And if they haven't failed, they're not exactly what one would call a success. Here's the catch. She has three couples she knows very closely, all three of which she feels are the greatest relationships she's ever seen. Her friend Mick...open marriage. Her brother...open relationship. And our marriage.