Consider the REI brand of bags. I'm a Western Mounatineering disciple myself, between my wife and I we own 5 of them. But man, are they pricy. Go that way if you can afford them (I suggest the 10 degree version, forget its name).
But we're talking $600 for that bag. The REI Magma, for example, is more like $400, and with a 20% coupon, $320, roughly half the WM price. I've heard nothing but good things from some close friends about those bags. This bag does have a bit less girth then some bags, if that's important to you (it is very much to me).
Just a thought if you'd rather spend $320 vs. $600 or so.
For the record, great quality gear, especially sleeping bags are worth the price, but I backpack all the time, year 'round so my "cost per night" is cheap even for WM bags.
Here's a link to the 15 degree REI Magma. It's probably similar in overall warmth to the 20 degree WM.
https://www.rei.com/product/148248/r...eping-bag-mens