No advisable to go for one these days. The market for Rx8s has seen a huge fall recently owing to almost zero demand due to the notoriety of the car itself.
But if you're interested, then the fair price would be around 1 million at max, as it needs lots of time and money to bring it back to a proper running condition. doesn't matter if it is 2003 or 2009. ruined engine means it is not an Rx-8 anymore. You might as well swap an engine in a ke-73 or a datsun 120Y and enjoy the same power at a fraction of the price.