I regretted every cheap bag. Have yet to regret the nice down quilts I've got. Less than two pounds and unfailingly warm. However, they work best in colder temps when tucked around you nicely.

If you want to thrash around in complete enclosure go look at Montbell Super Spiral bags - higher end, but some models are made with stretch for folks who move in their sleep or sprawl. Western Mountaineering is another high end bag with different options - you can find a semi rectangular in varying weights.

You really get what you pay for with bags... learned that the hard way. Pay once, enjoy for years... pay many times over when the bag is cold, the zipper breaks, the synthetic breaks down... You don't get cheap, warm and light all in the same bag. You get two of those. Pick your priority.