You can try different stem heights without cutting your steerer; you simply put spacers above your stem as well as below. You can then vary the height by shuffling the spacers and stem around until you find a height which suits you. Keep in mind that the combined height of the stem plus spacers will need to be such that the total height is about 3mm higher than the steerer so that the top cap, which is used to set the headset adjustment, contacts the stem (or spacers) rather than the steerer. If the cap touches the steerer you will not be able to properly make the adjustment. Once you are VERY sure you have the height you want you can then cut the steerer if you do not like having spacers above the steerer.

Sheldon Brown gives an alternative method which does not require spacers and can be used to find your preferred stem height here: http://sheldonbrown.com/handsup.html#threadless