Pliny wrote an answer about Lafuma Warm'n Light 800 Sleeping Bag: 30 Degree Down on January 12, 2013
Mine has the European standard range of temps on it. 41/32/3.2 F. But temp ratings are relative because of individual differences and differences in conditions (wind, humidity, tent size, clothing worn, and may physiological as well as psychological factors. It is all very confusing, but remember this. If a bag has same weight of down fill of the same quality (loft) then any average designed mummy will give you the same warmth. 2 lbs 2 oz of 600 down is adequate in my opinion for three seasons. I have no condensation problems and mine sheds water better than I would expect (and I don't plan on it). I think you are steering in the right direction looking at this down bag and ones of comparable weight.