Torchlight EXP 0°

I'm gonna ignore the 'cheap' part. Sounds like you want a 0F down mummy bag and a inflatable pad like a Nemo Tensor. I would definitely opt for a 'water-proof' down. the normal price for the pad is $200. a bag like that is can be about $700 but the Big Agnes Torchlight EXP 0 is usually under $400

yes, that is a lot of money. but it is about as light as you are going to get and still be comfy at 10F.

I spend significant time in the field and also western hunt all fall/ winter. I run a Big Agnes Torchlight 0 degree bag and a sea to summit reactor extreme sleeping bag liner when needed for additional warmth. Consistently comfortable in damp, very cold, and snowy conditions. Synthetic fill retains warmth even when wet and dries quickly. I also use my issue bivy when needed.

Check out the REI outlet online. The last bag I got there was from lightweight Big Agnes, and the discount was 40%. Great backpacking bag so far!

The Nemo spoon shaped bags, TR Boost or BA Torchlight are all nice and accommodating for flamingo type sleepers (I am one as well.) Also consider a quilt!

Since it's currently at full price, the Magma is about $100 more expensive than either of OP's choices. The big difference is that has 800 fill power down, where the other two are 600 and 650 fill power. My daughter recently replaced a synthetic bag she bought while in college with an REI model, and liked their new sizing system. I think she may have bought the REI Magma. I have and like a Big Agnes 650 down bag I've had for years, but at a 15 degrees F rating, it hasn't gotten a lot of use in recent years. I agree with u/TheBimpo that, unless they are trying to put a full set of gear into a pack of 50 liters or less, OP will do fine with either of their choices.

I would go with a quilt, they are great for moving around. Zenbivy is most peoples favorite, I really enjoy my Big Agnes.

If your biggest concern about a sleeping bag is room for your legs to move without feeling constricted, I would try out Nemo or Big Agnes sleeping bags. Both tend to have wider profiles. Definitely go for a bag that is rated at least 10 degrees lower - preferably lower - than the temps you expect to sleep in. Theres multiple problems with layering with clothing like this, one of which is not the warmth specific factor but the breathability. One or two layers is one thing, but with all the listed clothing and then something like the picture on top, you’re going to build up humidity near your body you can’t get rid of, and you’ll become even colder. Next, a sleeping bag basically creates a warm pocket of air around you. The insulation in the bag helps create and maintain this pocket. The more compressed this insulation, the worse it performs. With layering clothing, you compress the insulation, making it less effective. On top of that, insulation is minimal if not nonexistent at the seams. Some puffy jackets and “extreme temp” clothing gets around this by minimizing seams but there’s almost always a few somewhere, which means no air pockets and no warmth. If I could recommend the best case scenario for you, it would be this: find a sleeping bag you can tolerate rated to a temp appropriate for your conditions, 15F at a minimum, best scenario a 0F. Dress in only your smartwool layers, and make sure you have a good pad/sleep set up underneath you. Sources: avid outdoorsmen, backpacker in sub 20 degree temps, and former REI employee who specialized in camping gear.