I've used the Kelvin jacket. I find it to be over priced. It isn't very durable. I am usually an XL, but needed a 2XL, and it was still tight in the shoulders, short in the arms, and way too big in the bottom.(I realize that fittings vary for each person, but I usually have not problems. I am 6'1" 200 lbs. average build.) I have found a valuable resource for gear, particularly new gear: Captivatem Outdoors. Mike Monnin is the owner, and the guy you talk to on the phone. He lives in Barrow, Alaska. He has turned me on to a Montbell jacket which is about 1/2 the price of the Kelvin, fits incredibly well, and is as warm or warmer than the Kelvin. I don't know the weights, but the Montbell packs smaller.
The one draw back is that it has a nylon shell, so probably not quite as quiet, but more durable than the Kelvin.
I would highly recommend the Montbell for anything in Alaska, and sheep elsewhere. It probably isn't an ideal outer layer for elk or deer as it is a bit loud, however it is thin enough to use as a heavy layer in extreme cold.
I use some sitka stuff, and I like it. Particularly the Stormfront rain gear, and the Coldfront. Lawnboi stated that Sitka is revising the Kelvin, I would concur that it needs it. If you get it to fit you alright, it is probably an okay jacket, but I think you could find something just as good for much less money.