So, I'm a similar size to you - 5'11, 180 lbs, US12 boot, although I wear Burton Rulers which have footprint reduction so more like a US11.
Anyways, I've been down in Wanaka for the last couple weeks, have ridden my NS Proto 157 in a bunch of conditions. We had one 20cm pow day at Cardrona, my impression was that the Proto could handle pow, although you do have to work for it. It's a great all around board but I'm not sure it's gonna be the best option if you're hitting deep pow on a daily basis.
And on a (slightly) related note... at Cardrona a ton of the rental gear is NS! I've seen people with Proto, Legacy, and SL rental boards. Sure is a lot more flash than some of the rental gears I learned to ride on.