Do you have any place you can go and check them out like an REI or other outfitter? Have you looked up some of the reviews online as some of them list the size (height, weight, general build) of the testers and their feedback.

Bang for the buck the Marmot Sawtooth (650 down, nicely squishable) seems to have quite a bit of room if not entirely the room of my WM Alpinelite, but then I tend to spin like a top when I sleep unless it's in a hammock.