Basecamp Down Sleeping Bag 15°F

S2S do have their bags EN tested so that temperature rating is accurate, with the caveat being EN testing is done with the dummy wearing winter base layers, socks, gloves and a beanie. It is a skinny bag and not suited to larger people tho, I have the S2S "BaseCamp" the larger version of this bag and I use it for car camping and find the modelling accurate for me as an older camper who likes comfort

The last bags we had were high end sea to summit that were rated to 0 to minus 15C. They were rubbish. We bought Neve gear quilts. Very light, compact and the best things ever.  Much easier to get in and out of. We still use a liner/sheet sac. If you can afford to get them made, as opposed to off the rack,  do that.   Don't ever use your bags outside, especially next to a fire.  Thats only for instagram pics. Pick a bright colour for the inside and a dark outside colour. We use trekology blow up mats.  Exped deteriorate too easy.  We use our gear a lot. Usually go for 1-4 months and sleep out 90% of the time. 

I have a sea to summit backpacking bag that’s 15° rated and once it’s in a stuff sack it’s incredibly small for a 15°. Coleman is basically bottom of the barrel, sleepover style, when it comes to sleeping bags, I’m surprised you aren’t freezing to death at night.

At REI? Probably just the sea to Summit. Cottage brands just do a better job overall. Here's a good start, but there are tons of other options. https://www.garagegrowngear.com/collections/quilts-sleeping-bags?srsltid=AfmBOop9T_mFgmquiOSKZQgg1443MbZ_HlewD5AHWCbOT52ZRMPPJVRi

Knowing Kathmandu quality, this is likely as good as it gets with that bag. I wouldn't trust their temperature ratings. If possible, return it and buy a Sea to Summit or Mont or other brand sleeping bag. Sorry.

Never used a berghaus mate, snugpak is good for the price but I’ve upgraded to a sea to summit bag and a mountain equipment bag and can’t recommend either of them enough!

Quilts can get drafts, but then also sleeping bags compress and lose loft as you shift and expose the compressed side. About even in my experience. Sizing, quality of pad straps, or user error are all possibilities if you've had better luck with a bag over the quilt. Also, audio books with a sleep mask headset and ear plugs. Give a pillow a try as well. I use the better sea to summit version and it helped my sleep quality a lot.