If you poke around the interwebs, there are some good clearance deals on the Golite Venture 0, a 800 fill bag, 3lbs 1oz reg (3lbs 3oz long), 7inches loft.

I just picked one up for $275, but have not tested it. Construction looks good, zippers alright, not great. But if it were me, for the same money, same weight,I would expect the 800 fill to out perform 600, leading me to think the LLBean is probably over rated.