
NEMO
Disco 15 Series
Spacious for side sleepers; bulky, temp rating optimistic.

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Same -- two EE quilts; a double for when wife and I go together, single when we're on solo adventures. Been a good purchase for us.
We have two EE 10F quilts; one is a double (Accomplice), the other is a Revelation for when one of us goes solo. Been very happy with them. We've been down into maybe around 20F in them and were fine, but you're going to want some decent head warmth like a down hoodie or an add-on sleep hood like their Torrid hood. I'm a side-sleeper and roll around a lot. I typically put a ZLite on top of my air pad for extra warmth and improved sleep profile, and use the EE pad straps to keep it in place. I don't usually use the quilt clips to secure the sides of the quilt unless it's really cold. We've had our Accomplice for at least seven years now and it continues to perform well. Only had to wash it once so far (which is actually a pretty lengthy process to do it right).
There are many…from REI house brand, to more expensive (hipster!) cottage brands like Enlightened Equipment, Zpacks, Zenbivvy, Katabatic etc etc. I have 2 Enlightened Equipment ones - chose them as they are cheaper than some other niche brands, lighter than nearly all others, and have good resale value. I have a summer 40F quilt and a 2 person (!) 20F quilt.
I sleep rather cold. I could never make a quilt work for me I says wanted the sleeping bag hood and no air drafts. So it’s the Xtherm and western mountaineering versalite 10 degree F or ultra lite 20 degree F bag for me in almost any US mountain west situation when I’m alone. I think western mountaineering is king sleeping bag maker in the USA. You Could look for used or sales on the Bags because I think they’re more than $500. When I hike with my wife I do a 10 degree accomplice double quilt from Enlightened equipment. I do find the other body heat helps. We tried a ff spoonbill which has a hood but it didn’t work as well as the quilt with two. So I have to be mindful of drafts. As others said eat something before bed, pee, and eat something else at night if you wake up cold and pee if you need to. Also there’s some argument to be had for naked sleeping in a sleeping bag that’s warm enough vs wearing puffies to sleep in. I personally always wear down pants and jacket to sleep if it’s cold. Also campsite selection can contribute to cold.
Two sleeping pads + sleeping pad coupling straps to hold them together (OR the thermarest luxe coupling sheet, not UL but it was a game changer for us) + 2 person quilt. My husband and I use the thermarest neoair xlites and the enlightened equipment 2p quilt. We love being able to cuddle but also separate ourselves or sprawl onto each other's sleeping pads. Edit: I'm not sure if you asked for a tent recc but we've been enjoying the durston xdome 2
If you’re car camping just bring blankets. For backpacking my wife and I have an enlightened equipment double quilt. Very warm, very light. But let tell you: sharing a bed backpacking and sharing a bed at home is not the same. And the bag is larger so packing is a little more complicated
My gf and I use an Enlightened Equipment Accomplice quilt with a Big Agnes double-wide pad. Since the quilt doesn't have a bottom, we use a Klymit double V sheet to put something between us and the pad, though it's the same size as a twin mattress, so before the Klymit we were just using a fitted sheet. We are both relatively small people, so this setup is comfortable for us. We can be close, but since the sides aren't zipped, we can kick a leg out or leave a side open if one of us gets too hot. This has worked well for us in a variety of temperatures.

NEMO
Disco 15 Series
Spacious for side sleepers; bulky, temp rating optimistic.
Hammock Gear
Classic Burrow 20°F
Budget king; very warm but heavier than ultralight.

NEMO
Disco 30
Spoon shape for side sleepers; prone to zipper issues.

Western Mountaineering
VersaLite
Durable, very warm; premium price, too hot in summer.

Katabatic Gear
Alsek 22°F Quilt
Versatile 3-season quilt; secure pad attachment, high price.

Ranked #1
NEMO - Disco 15 Series

Ranked #1
Kelty - Tru.Comfort Doublewide 20
Ranked #1
Enlightened Equipment - Revelation APEX

Ranked #1
NEMO - Disco 15 Series

Ranked #1
Feathered Friends - Egret UL 20/30

Ranked #1
NEMO - Disco 15 Series