IMO, the best sleeping bags for you are going to be the ones with Polarguard Delta. They don't compress quite as much as down (although they still compress a great deal), but they're still very light and they insulate even when wet. The big name companies all make good bags using this fill. For my money, I would buy the North Face Cat's Meow (+20 rating) without hesitation. It's one of the best bags made. I currently own the North Face Snowshoe (0 degree version of the Cat's Meow), and I love it. You really don't need a 0 degree bag for that time of year, though, so the Cat's Meow would be perfect. If the temperature drops below 20, just sleep with your clothes on. I have a 25 degree Polarguard 3D bag that I've used in sub-0 weather multiple times without any problem.
http://www.rei.com/product/746449
BTW, Polarguard Delta is the improved version of Polarguard 3D.