I've seen "incredibly strong" monogamous partnerships fall apart. Not all, obviously, I'm not anti-monogamy. But polyamory forces you to work on your issues, to face jealousy and insecurity, to get better at communication and time management and acceptance than you were before... if it's going to work, that is. It's sometimes semi-jokingly called Relationships 201. I figure, if you're forced to work harder on your relationships skills, maybe you'll get better. Maybe you'll actually deal better when a storm comes your way than you would if you'd never challenged yourself.
That's not why I'm poly, precisely. I'm poly because it feels right and natural to me. *shrug* I find that I get different things from different partners. I learn more about myself. And, hey, more people to help out if I need to move or hide a body.
I'm out, so the closet isn't a problem for me. Why do you feel like you guys couldn't possibly be out?