I can't imagine that your wife consented to date you, and then marry you, just *because* you were single, sane, and solvent. You call it a "trump card", but if that were so, why wouldn't she have hooked up with the first interested man she met who had those same qualities... surely you couldn't have been the first man she met who possessed all three? You talk about that combo like it's some extremely rare thing, but in my experience it's really not. Also, believe it or not, there are plenty of women who like serious, intellectual, unconventional men. At least, there are in my world of female friends who are geeks, computer programmers, scientists, medieval enthusiasts, non-profit employees, artists, etc. Maybe you were just hanging out with the wrong crowd before?
You're still sane, you're still solvent, you're just not single, but a woman who's poly, who may very well have a marriage of her own, isn't going to have a problem with that. In fact, I get the impression that some partnered poly people prefer, when they form new entanglements, to get involved with people who are also already partnered, so that they don't feel responsible for fulfilling a role in their new partner's life that they just don't have the time or logistical ability for.
Whether you believe the things I've written or not, just go ahead and jump in. Maybe you *won't* find a gf, maybe you're right. But it'll be diverting to look, yeah? Just try to project some degree of confidence... if you do find an interested woman, don't tell her how puzzled you are that she's into you.