The Firstlight looks to be a very nice jacket and it sounds like it'll do most of what you want. I bet you can get it for less than $400 if you can wait for a sale. It's water resistant, not waterproof but IMO that's a good thing; I want my waterproof shell to be separate from my insulating layer so that I'm not wearing the shell all the time. The one I use as my "warm jacket" has been a puffy jacket made by Mountain Hardware, the Chugach but they don't make it any more. It's not as nice as the firstlight though.
PS, here's a little unsolicited advice related to this:
What I've don't for elk in the past is pack my coat in then put it on in the stand (carhartt by the way). .
I'd be willing to bet you grew up hunting whitetails. Hunting "on-stand" is a good strategy for whitetails but rarely is for elk on public land. When I moved to CO it took me a couple years to figure that out, and to figure out that my success rate went up exponentially once I stopped hunting stationary and started moving until I found animals. Sneaking within range of elk and getting a good shot opportunity out west is much much easier than sneaking within range of whitetails back east. The footing is much quieter and the animals are not as paranoid. Plus, elk move around to different areas at the drop of a hat or for no reason you can discern. You can be hunting over really heavy sign but the animals have moved out. So the heavy jacket is almost always in my pack and I'm normally wearing much more svelte layers for 95% of my hunting.
