The 6100 come in 4 different formats. The 6140 is the smallest model and the firebox will of course be the same on all 4 models.
The 6143 has a taller log store under the stove making the height 950mm.
The Morso 6148 is a pedestal model and gives a taller firebox. This in turn makes it easier to feed the fire as you do not need to bend down to reach the door handle.