I realize this probably won't help much but I'll throw it out there anyway. I personally feel like most ski equipment is a commodity now for most people until you get up into the pro level. As long as the skis are sized correctly for their type (shaped, all mountain, powder, full rocker, stiffness, etc) and to the rider height and style, that will put most skiers in a good spot without having to worry about brand.
The nice thing about that is that skis can now be purchased used craigslist, at sierra trading post, evo, etc. I've skied multiple brands and types 50+ days a year in the backcountry and front, and they all work just fine, IMHO. I usually buy whatever is cheapest and then ski the crap out of it
Now to your specific use. For a good all mountain type ski, I'd go with something with an 85-95 waist. That will be fairly stable in powder and crud but too difficult to get up on edge on hardpack. Those Sin 7 skis are on the upper range of that so I think they'd be just fine, albiet a bit more powder oriented.
Given that the sin 7's are a rocker'd ski, you can ski them longer than normal skis. The benefit to this is on hardpack, they have a short effective edge because the rocker doesn't touch the snow. Easier to turn, more nimble. But in the powder the rocker tip/tail provides more float. I think you'd be fine with a 172. You may also get by with the 164 but its personal preference (IMO the 164 is a bit short in that style of ski and won't feel as stable as the 172).
For your use I'd go with the sin7 over the soul, my general feeling is that anything over about 95mm waist (about the width of a ski boot sole) gets progressively harder to get up on edge. I've got a pair of BD Amperage with a 115 underfoot and its noticeable from my 92mm underfoot rossi's.
And no input from me on downhill bindings...I've no experience recently due to tele.
hth! Its a great year to get new powder skis, and we're not even to the snowiest month yet!