Lots of good quality brands mentioned and down vs. synthetic comparisons. Thought I'd kick in my couple of cents worth of opinion as well!
I have a Cabellas Holofil, semi mummy bag that is 30 years old and originally rated for -20F. Undoubtedly, it's lost a bit of capbility at the lower end of the range. It's in top shape with heavy use. I kind of toss things around and don't baby it. I've never been cold in it in temps going down towards -10F.
As a comparison, I bought my son when he got out of high school and very fine Marmot down bag and have tried it out a few times. About busted my butt sleeping from the normal bumps and knobs that always poke in the wrong places when tent camping. The down compresses to almost nothing between you and the ground so there is no extra oompf to help the waffle sleeping pad or the self inflating matress.
IMHO, Since you're style is going to be towards tent camping, this negages the lighter weight and smaller stuff size advantages of the down. I am definately biased to holofil for tent camping.
For sure, try on any mummy style bag for size before buying. Way too many of them are way too confining for my tastes. My modified mummy has lots more room than is typical for the classical mummy.
Where I have evolved with for my tent camping, not backpacking, is actually using two bags. I have a cheap Colman rectangular from Walmart for warm weather and I open up the Cabella holofil for a tent floor cover to lay on. In cooler weather, I reverse this and use the cheap Colman for the floor liner. This really cozies up the tent.
One of the folks mentioned the multipiece military sleeping bag system. This is sort of what I have cobbled together for my routine gear and if I was buying new now, would give a really serious look at this setup.
I am very negative on any rectangular bag for cold weather use, no matter what the quality of contruction and insulation. No matter how much you burrow down in it, cold air is going to sneak in down to where you're hidden. LOL!