A couple of comments:
Your lack of experience is a major problem. You got some good advice here, but you need to talk to people who hike in the area you will be camping in and ask their advice on the subject. I looked at the Aegismax 800. At 14 ounces I am very impressed. At the price and weight I might purchase one as a sleeping bag liner for winter! However, for a three season bag the ratings are not what I would ever consider as a main bag. The light weight is because it has less fill, therefore less loft. However, having said that: while there may well be a relationship between cost and quality generally speaking, some of the bags in this thread blow my mind in that they look pretty good and have good reviews for the cost. And...I don't think the curve I a straight line. At the high end I think you pay a lot more for just a little better quality. Two of my friends have the very best Feather friends and Western Mountaineering bags and paid more but don't sleep any warmer than I do in my North Face which is an excellent high end bag, but I didn't pay as much as them. I think North Face has some of the highest quality bags on the market at less $ than some others.