What Will Happen to the Balance of Power?

Saddam Hussein was one of the meanest Arab dictators. He deserved to be eliminated, and his evil regime deserved to totally be destroyed. However, the question the US should have asked - by doing that what will happen to the balance of power in the sub-system of the Persian Gulf, between Iran and Iraq? If Iran is the bigger Satan and Saddam's Iraq was the smaller Satan, but they balance each other, what will happen if you take out the balancer, Iraq, and leave alone the revisionist power, Iran? By that you endanger other even more important players in the region. If you have an alternative power in the region, or you believe you can build a stable regime in Iraq, than it was not only legitimate and justified to topple down Saddam regime, but even a must. However, had the US an alternative?