I think you need to wonder what you are looking for, really. Sex? Emotional connections?
Even if the problem is that your wife isn't filling your emotional needs, it could be because she can't. You might have emotional needs that can't be filled by a single person.
I would say it is always worth trying to work out existing relationships. However, if you truly are poly-wired, you might find yourself unable to be with someone who can't accept that. If that's the case, you might have no option but to break up, and in future relationships be clear from the start.
Do you know what problem your wife has with the idea? It could be based on misconceptions. You say you've talked about it for six months though so I guess it's doubtful. Still you might be able to work things out if you take your time... It was hard for my husband at first but we worked things out.
If you break up with her, I think it is a good idea to do it now, when there is nobody else in your life, so that she can know it's about who YOU are and nothing else.
Me: 31F, straight
Seamus: My husband, 32M, straight
Dragon: My boyfriend, 29M, pansexual, married to Fox
Fox: My boyfriend, 29M, homoflexible, married to Dragon