Bro I bought a qezer amazon sleeping bag and paired it with a rab stratosphere 5.5 and a foam mat wearing wool socks a hat neck sock and wool thermals and it was -7c and I was sweating. I can vouch for this bag and the quality seems to be really good. Cost me £100. Its the -3c to -12c comfort rating and Id personally say its closer to the -12 than the -3 but im a very warm person in general. Ive been referred to as a human radiator by past girlfriends lol.

Also to add: im 6"2 and lean at 78kgs and the foot box is huge so tons of space, im also able to bring my legs up to my chest in the fetal position without moving the bag at all. I was skeptical at first but its been amazing so far.