Aer lingus doesn't fly to Warsaw, they're starting in June. There is no direct flight at present. KLM go as do BA, Lufthansa, LOT (polish airline), and a lot of others. Try ebookers.ie to see all flights. They all stop off at different places depending on the airline - Amsterdam, Zurick, Frankfurt etc.
The only airline that fly Dublin to Warsaw direct is Aer Lingus. However having just checked their site - it does not start operating until 01-06-2004.
Did a search for a flight in June - €163 return - seems pretty reasonable to me!
Never been to Warsaw myself.