Col Sleeping Bag

With used stuff it can be a little harder to see year to year differences. If you can find specs for the EN rating and you are a cold sleeper gonfor the comfort rating. If you are a warm sleeper go for tge lower limit. Those are all probably good mid range brands though can veer more fashion at times. I like Marmot bags bit the Col looks pretty gimmicky. The rating for the Big Agnes brand shows it to be nominally rated between the lower limit(warm sleeper comfort) and extreme(survival) rating. That kinda puts it in Coleman class but for me would probably be plenty warm in your described conditions. The 600 fill down though is going to be a lot bulkier and heavier than the 800 fill power stuff in the other two bags. 

I have a Marmot Col -20. It’s quite narrow, especially compared to my zero (marmot never summer) and 15f (Nemo disco) bags. I almost bought a CWM a couple years ago but decided that the Col is all I’ll ever need in New England. If temps will be colder than that, I’ll change my plans.

The Col is awesome.

That is a baller ass bag. The REI in Ann Arbor, MI had one in the Re/Supply and I was going to buy it, but it was a short length bag. You will sweat your butt off in that thing for normal camping. However if you like to go camping in 15F or below temps all the time you will be plenty comfortable warm. I wouldn't use it for anything above 15 or 20F, especially if you are a warm sleeper. I have the Marmot COL -20F bag. This is my go to bag for anything under 15 or 20F. Around freezing I use a Hammock Gear 0F quilt. The next question is what pad are you using? If you are going into extreme cold Canadian winters you should be looking at getting a Nemo Tensor Extreme, Exped Ultra 7 or Dura 8 or the Thermarest XTherm. A super warm bag won't do anything for you if you don't have a well insulated, high R value ASTM rated pad for the ground. I would also check the r/moutaineering subreddit for their opinions.

I've had a WM Kodiak (0° down bag) for probably ~10 years now? The *only* time I've experienced a noticeable loss of loft was when I spent like a month living in a car during November in the PNW. Easily fixed by a dryer at the laundromat. On that note, make sure to read up on washing your bag when you do. If you're not careful you can blow out the internal baffles that keep the feathers in place. Drying from completely soaked is also a bit of a process, lots of stopping the machine and breaking up clumps til completely dry.

Yeah it's been a fantastic bag and I've had a shit ton of nights in it. Probably my favorite piece of gear I've owned. My Marmot Col though(I forget how old, but when they still had the side zip). Shittiest. Zipper. Ever. Absolutely would have returned it except I got it on a pro deal. The shittier part is that since it's so bad, it's almost completely unusable when your fingers are cold.. Which is mighty inconvenient in a -20° F bag..

Im generally looking at higher-end bags that are available second hand with minimal use, cr completely unused. Some options im looking at are TNF Inferno, Marmot Col, and Big Agnes Greystone

I'm a big believer in over warm sleeping bags. I have several depending on the weather. The one that stays in the back of my truck is a high quality -20 Marmot bag. I can unzip if warm and bundle up if cold. INCHES OF LOFT is the key to being warm. Not blankets. Down, lofty down. Inches of loft is the key.

Western Mountaineering, Feathered Friends or Marmot for bags. Enlightened Equipment, Hammock Gear or Katabatic for backpacking quilts. Not cheap but quality and comfortable.