I had to comment - the Always Summer at the link you have is nine dollars more than I spent on the Never Summer, a 0 degree bag with a lot more down in it! If you haven't tried Sierra Trading Post and got on the Deal Flyer, you may be missing some excellent deals on bags.

Too many people have told me their Mountain Hardwear bags aren't warm enough. I'd go with the Marmot or Kelty - both are EN rated about the same, 50F comfort rating, so I'd go with the lighter of the two. Or, go with the Campmor branded 20F bag, which is more realistically a 30F bag in practice, and spend about the same as you would on that Kelty. It's always easier to open zippers or use the bag as a quilt than to make a cold bag a warmer one.