I haven't skied those models, but in talking to the Volant rep at Loveland last Saturday I got the impression that the Machette Truth, Genesis Gold, and Gravity 68 were roughly today's equivalent to the Ti Powers, T3's and Machette G in the all mountain category. The Soul appears to be a pretty heavy duty free ride ski for the steep and deep similar in intent to the Machette McH (but with more side cut), the Gravity 71 similar but a little more easy going. The 71's and the Souls have a wider footprint, so they should be a bit better in powder than the Truth and the 68.
Last spring I had a chance to demo the Gravity 66 in a 175 length. I think this fits into the product line about where the Supercarve did. If this ski is any indication I would need to go shorter with the new product line than I did with the old ones. I'm used to sking on 183's, and the 175's felt too long! I also tried the Vertex 68 in a 165. It was fun ski - stable, quick turning, and it blew through the spring crud very nicely.