I believe Iran's motives are not to destroy Israel, or to lead to a war with the 'West' at all. Instead, Iran is trying to become the center of power in the Middle East, a position currently held by Saudi Arabia. Both countries absolutely hate each others guts for a variety of reasons, a main one being their religions; Saudi Arabia is mainly populated by Sunni Muslims, and Iran is Shiite.
Right now, many political and business dealings are done through Saudi Arabia. Essentially, if you want something done in the region, the people who will do it for you are the Saudi's. With this power, Saudi Arabi is seen as the representative nation for the Arab population, and Iran would like to take that crown. Iran's rhetoric towards the West, and Israel is similar to Egypt's attitude during the Nasser era. Nasser gave stirring speeches about uniting the Arab world under the banner of Pan-Arabism which would overcome Israel; however, it was merely a domestic, and foreign policy ploy in order to get respect on the world stage as Nasser really had no desire to wage war with Israel at all, because he knew Egypt would not have a chance in hell of winning, and they would lose even more territory to the Israeli's.
In my opinion, Iran is merely repeating history. Ahmadinejad has adopted a populist stance which is confrontational, and bombastic... but he is a paper tiger. He appeals to both Pan-Arabs, and the Pan-Islamic crowds, much like his predecessors Nasser, and Hasan al Bana. Iran has no desire for a war with anyone. Trade between Iran and the United States has grown almost ten fold under Bush. It still pales in comparison to trade with China or Canada, but it's still money.
The uranium enrichment is just one way to rally Arab's around Iran, because it allows Iran to puff out its chest and look tough. The leaders of Iran are smart enough to know that if they do launch a nuclear missile, or allow a terrorist organization to get their hands on one, the Middle East will be a sheet of glass within a day. Plus, on the bright side... Iran hates al-Qaeda because al-Qaeda is full of Sunni's, and we all know how well those Shiites, and Sunni's get along.