For $100 down is out the question, which means that what most on here consider light is also out of the question, and I still don't know what temps you need to cover. 20 deg for 100 means a discount marmot trestles 15 on sale, but is about 4 lbs. Move up to about 150 and you can drop down to 2.75 lbs and a North face cats meow on sale. Move up to 200 and you can get a closer to 2 lbs or move up to 30-35 deg at $200 and you are in 750 power down or better territory on sale which means you weight can come way down. I have a montbell super stretch down 30 bag and got it on sale at 210. It is 1.5 lbs and stretches to near semi rectangular bag measurements. At $100 dollars if you want anything for a 35 deg setting, you will have to buy the rayway book and make it yourself, which isn't a bad option.