Trek

Capisco il dubbio sul discorso umidità, ma con quel budget andrei comunque sulla piuma, ormai hanno tutti un trattamento idrorepellente e la leggerezza ed il poco ingombro sono per me impagabili. Io ne ho due un naturehike cw295 (comfort 11°) ed un seatosummit -1° entrambi in piuma e non ho avuto nessun problema nemmeno nelle notti più umide dove ho ritrovato la tenda completamente fradicia. Vero che costano di più ma per quella temperatura io ti consiglio il naturehike che ho io, lo trovi a meno di 100€, è leggero e non è a mummia quindi secondo me molto più comodo. Ricordati sempre che la temperatura comfort non conta niente se non hai un buon materassino isolante, ovviamente in estate te ne rendi meno conto ma se le temperature si abbassano te ne accorgi eccome.

Materassino non so come sei messo ma io sono passato dal forclaz 3.3 al naturehike 5.8 ed è troppo più comodo. Come sacco su quella cifra si inizia a trovare diverse cose, c'è da vedere se è disponibile la taglia adatta a te. Io ho il seatosummit trek2 comfort -1° non è nemmeno dei più leggeri (circa 900g) però è comodo perché non è proprio a mummia ma leggero più largo, mi sa però che non lo fanno più, io l'ho preso un paio di anni fa a circa 200€ in offerta. Fai una ricerca filtrando magari prezzo e dimensioni su pack wizard.

Sea to summit ascent and trek (older version) is what I have. I got the long versions in each flavor. My wife has the female version. They're so good IMO that when they were being discontinued we picked up extras when REI had them for 50% off. I'm likely not going to be buying new bags for a couple of decades now....

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 disco 30, M44. I went camping in May (65°F low) and September (60°F low) and was too hot, had to unzip and use like a blanket. I also went further North in October (45°F low) and was comfortable. My daughter has a Sea to Summit (30°F) and she was cold. Liners are an option but a royal PITA if you have to pee at night. In hindsight, I'd have gotten a lightweight quilt for warmer months and a 15°F for her.

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.