From where I live (near Melbourne) I will beat you to the Gold Coast flying my 165 kt machine than if you take RPT
You might want to reconsider your times there. On your own figures I've got the jet beating you by over an hour already and that's not considering how long it takes you to drive to your local airport.
GA only really beats RPT over a short distance. SYD-MEL is about it beyond that the jet speed kills most turboprops/Pistons