I think W_D has a good idea on the Primaloft. In the very wet conditions you're liable to encounter (from reading, not experience), you may be able to keep the down dry, but it will be a lot harder!

Do remember, though, that once the Primaloft gets wet, it isn't any warmer than wet down! You still have to keep the jacket dry! The difference is that synthetic insulation absorbs far less moisture from the humid air.

I'd use a synthetic base layer (such as Patagonia Capilene) rather than silk, which has little warmth. The advantage of Capilene over wool is that wool absorbs moisture, but Capilene absorbs a lot less. Wool, however, feels warmer when wet.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey