No, I believe there are four Acts in the game. Blowing up the Citadel isn't an official quest, it's just hinted at as a task that could be done!
Regards,
Michael
It's In the kichen where the cook ask's you do do something about the Rat problem.. If I remember right! <img src="/ubbthreads/images/graemlins/think.gif" alt="" />
