I'm not sure there's much we can do about Iran obtaining nuclear weapons. There's the economic sanctions option, but I doubt that will be effective. They didn't work against India when they were working on nukes.

The US military is too overextended to be able to pull off another regime change. The rest of the world is probably not going to do what's necessary to stop them.

I really don't see a good solution here.

We need to stop being hypocritical with our policy regarding nuclear weapons. You can have them....you can't. Who are we to decide? Iran knows that if they have nukes they will be part of a very exclusive club that gets to say "Don't fuck with us.". Not to mention the fact that we're occupying 2 of the countries that they share a border with. I'm all for a regime change, and I don't feel very comfortable about a religious theocracy having a nuclear stockpile; but the last thing we need right now is another war.