Hi Rotem, I happen to own the Marmot Ultra Elite 20 in the regular size and have used it quite a bit. The temperature rating is for real. Marmot gets it's bags EN tested. This one got a EN13537 lower limit rating of 22.5F and a comfort rating of 33F.

I've slept in it down to the low twenties wearing a base layer and a puffy jacket and been fine. You're a lot younger than I am and probably run hotter, so you're likely to be fine with this bag.

One reason this bag is warm for the weight is that it has an efficient cut, so you have to know if you're OK with that.

Also, the actual weight of my bag is 34.8 oz which is 2.8 over Marmot's stated weight of 32 oz.

Premium synthetic bags like this will be discounted occasionally, so if you're patient you can get a good deal. I think I paid $150 for mine.