According to the Ducati stats, the 1000 has 18 more ft lbs. of torque and about 20 more horses than the 800. Having ridden them both, I would say you can definitely tell the difference. The 800 responds to throttle input with some real urgency; the 1000 responds like a sledgehammer to the forehead. Definitely be ready if you whack it hard or you may find yourself lying in the road.
With that said, the 800 has plenty of power for normal use, and the wet clutch makes for easier launches. They are both great bikes.