The pilot reported that, during landing and just before touchdown, the stall warning horn sounded but that he briefly thought it was the "gear warning annunciator." Thinking he had not lowered the landing gear, he rapidly increased the throttle to produce full engine power in an attempt to go-around. However, he did not apply sufficient right rudder inputs, and the airplane deviated to the left and drifted over grass past the edge of the asphalt runway. Further, the airplane had not attained sufficient altitude to clear rising terrain, and the propeller tips hit the terrain, the engines stopped, and the airplane slid on the grass. The airplane sustained substantial damage to the lower fuselage. Additionally, the pilot reported that he should have relied on the "three in the green" before attempting a go-around. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.