I wish that I had your self-knowledge when I started down my "road to polyamory". I could use some timey-wimey trickery to go back and do that properly the second time around.... You have quite a few things going for you, and I applaud you for your approach.
Here are a few things I see:
* You have decided that your marriage is more important to you than having multiple relationships. I deliberately phrase it that way rather than saying "not being poly", because you have decided that you most definitely are poly, and are choosing to not act on it, respecting your marriage vows with your wife.
* You have done a lot of reading and thinking before doing anything. So many folks have a "gut feeling" and end up "falling into poly", which invariably causes massive crises and the ensuing heartache.
* You care so deeply about not hurting your wife. You'd be surprised (well, maybe you wouldn't be) how many people allow NRE (New relationship energy), the promise of it, or the desire for it, to completely blind them to their current relationships.
* You have learned about what a relationship means, and are applying it to your current relationship. Again, this is something that so many forget in their rush to find someone new.
There are probably more points, but kudos to you so far.
One way of bringing up the topic is not to make is about you or your relationship. If you have friends who are non-monogamous, they can be a great example. Or you can find some sort of news article about a polyamorous celebrity that you read about. Carla & Nicolas Sarkozy, Will and Jada Pinkett Smith, Brad Pitt & Angelina Jolie, if you're feeling more scientific, Erwin Schroedinger the founder of quantum mechanics, Eric Schmidt (founder of Google) and Kate Bohner, Tilda Swinton and so on - I'm sure you can find an example that would fit your purposes. This way you can gauge you wife's reaction...
Another person I was talking to who I didn't know so well was talking about alternative relationships (she meant same-sex), and I said that as far as I was concerned, as long as folks were happy I didn't care if they were same-sex or non-monogamous. Her instant reaction was that same-sex was fine, but that monogamy was non-negotiable for her. Pretty good sign that I didn't need to bring up the concept of polyamory to her.
None of these involve lying, which is a good thing. If she asks you about it, you can answer something like "it certainly sounds like an interesting idea, but I would imagine that it would take a lot of work to make it function properly", and so on. If this goes well, it will open up a conversation about all these thoughts that you have been having about how relationships could work, both monogamous and polyamorous. If you get shut down with an "ewww no!" then you know that there's no point in going further.
Does this make sense?
"Listen, or your tongue will make you deaf." - Native American Proverb