On descent through 8,000 feet, the engine of VH-DBX started running rough. The pilot carried out the emergency check list procedures and found no response to throttle so he shut the engine down. Melbourne Flight Service (FS) was then informed by the pilot of his intention to land short of Goulburn. Another aircraft in the vicinity, VH-RPO, was diverted by FS to render assistance. The pilot of DBX did not declare an emergency, however FS initiate a Distress Phase. On short final to the selected landing site at approximately 20 feet AGL, the aircraft contacted a power line, rolled to the left and impacted the ground in a nose down attitude. The aircraft was then vacated with nil injuries. The pilot of RPO informed FS that an ambulance was in attendance and the Distress Phase was cancelled. A report has been requested for the engine strip and inspection.