The only true 30 degree bags that will stuff small are down bags. Kelty makes a couple for around 120 bucks that look nice. THe cheap quallofill bags that stuff to small sizes are usually overrated for temp. And are really 40-50 degree bags. A real 30 degree quallofill bag can stuff down to about 8 x 16 inches. Or maybe a bit smaller if you really compress it hard. However a good 20 degree down bag can stuff down the the size of a loaf of bread. Maybe 6 x 10 inches or less.

From my experience the really cheap bags temp ratings can only be assumed if you are wearing pants, long johns and a coat inside the bag. If you only have minimal clothing on inside the bag raise the temp rating by 20 degrees. The better bags usually have a somewhat more accurate temp rating.

You might check out something like this:

http://www.campmor.com/outdoor/gear/...0&CS_010=43124