I agree with Frank. Higher seems to sound better. And differences in height is quite dramatic.
I have a pair of 3.2s as well. I tried angling the speakers up and having the fronts higher and the back lower and angling the speakers down by having the fronts lower and the back higher and the sound wasn't good at all. I ultimately just left it at the highest position.
I haven't tried some microadjusting of the height however, so I don't know whether highest is the best possible. But my attempts at changing the height of the feet have been so discouraging and I get such a good sound from from its current height position that I just left it there.
I might do some more experimentation later as changing the height of the feet changes the sound quite dramatically or maybe I just overdid it :D