Funny old thing, I've just gone through this mill. I was in the Atlas last October. I stayed in bog cheap hotels and auberges. None of these were heated. Coldest was up in Agoudal. I took a 3/4 season bag and was too hot. This was a Jack Wolfskin blackbird. I was usually in the buff inside the bag.
I'm going again this October, so was looking for alternatives. I wanted something cooler, but also some flexibility in case there is a cold snap.
My solution was found today. I bought a Rab Travelite 300. Its on sale at Field and Trek for £75. I'm using this with a silk liner (this takes the comfort zone for the bag down about 2 - 3 degrees). I can also use the silk liner on its own if its really hot. The RAB's zip can open all the way around the foot box, so you can vent your feet, or use the bag as a quilt. If its mad cold I will wear clothes in the bag. Was thinking of buying a very thin down jacket (from PHD) for evening wear, but this could take the bag's comfort zone down to about -5 degrees for me. My feet never get cold, but my arms and shoulders usually do.
All this lot packs up to less volume (compressed) than the compressed 3/4 season blackbird. This is important to me as I'm on a bike. I think its a very flexible solution. Will let you know how it works out.