Presently, I use a Nunatak Arc Ghost (lighter than the Arc Alpinist and rated to 32 degrees). I tend to sleep a little cold, so the rating on this "variable girth quilt" seems more like 40 degrees to me. Of course, with a lightweight bag like this (I used to use a WM HighLite), my clothing plays an important role. My down jacket is the Hyperion by Feathered Friends (comparable to the WM Flight) and I wear this to bed on colder nights. Also, I recently swapped out my midweight capilene long underwear bottoms for a pair of Mont Bell U.L. Down Inner Pants. Here's my reasoning:
Since I wear hiking pants (instead of shorts), I find I really don't need my long underwear bottoms for hiking on cool mornings. Besides, I can alsways put on my rain shell bottoms (GoLite Reed) to block wind and trap warm air. So, I really only wear my long underwear around camp and to bed. And since the down pants weigh only a half ounce more than the capilene bottoms, I end up with WAY more comfortable camp insulation and can extend the range of my quilt significantly when Jack Frost comes a nippin'.
Also, having a lightweight layer of down around my body beneath the quilt helps to cut back on those middle-of-the-night chills as a result of drafts which are common with quilts. Of course, when it's warmer, the down pants and/or jacket make for the most luxurious pillows around.
My quilt, in a long, with am Epic shell weighs 19 ounces. My U.L. Down Inner Pants (which replace the Capilene bottoms I was already carrying) weigh just 8 ounces. My jacket (which I was already carrying) weighs around 11 ounces.
Since I can wear half of my sleep system, I can be comfortable over a wide range of conditions - and especially toasty around camp. Plus, I don't hesitate to jump out from under my quilt on chilly mornings as I'm already wearing half of my insulation.