User Review: Western Mountaineering Bristlecone Super MF
This is hands down the best bag I've owned. I'm a big guy as well and it is extremely comfortable and warm down to 15 below. It can be used as a blanket on a bed or hooked up to another bag.
There are so many ways to control the warmth that you can vary the temp inside the bag for summer or winter depending on how you configure the zippers. It's like a fluffy heated cave that has plenty of room for cloths at the bottom of the bag and keeps them nice and toasty.
You will not regret this bag by any means. It is worth every penny.