I have a Gaupner 800 drive the same as the one in your post on the back of a Graupner B24 'Nimbus' Bat boat and it seems to be pretty good performance wise to me, running a Graupner 700bb turbo through it on 12 cells and i get 32 - 35mph and run times of a good 15 minutes, i think the scale look is fantastic and although its not as fast as a direct drive if your into the scale look its still plenty fast enough.
Jon