Ohiohiker

Quality is a difficult thing to put a finger on. I have LLbean full zipper packlite pants that are very light, rugged, have never failed me and are my constant winter companion. I like their guarantee. Marmot gear is also excellent, BUT I have had 2 marmot jackets (expensive ones) delaminate and they replaced one, can't replace the other but they did offer to try, and one Marmott coat made in China was made with an inferior zipper apparently substituted in China, they replaced the zipper.

BUT what you want to know is 2 things - what is the loft of the bag since thickness = warmth almost, and which bag will fit you the best since your body size and how it fits the bag is absolutely as important as brand, loft, or the value of the down, OR ITS TEMP RATING. I can attest that 550 down can be very warm and rugged. I also had a US mountain regular military bag with a fill of "chicken and water fowl feathers" that had a militarized cotton shell, and is was perhaps one of the warmest most comfortable bags I've owned.

Look for a bag with a good "foot box", any quality bag will have good one designed to contain feet without them pushing into the bag and freezing your toes. If you need to wear socks in your bag in conditions warmer than its rating, keep looking.

Also these bags last forever unless someone destroys it washing it in detergent and a used bag 10 years old may still be an excellent bag.
Jim