Hi, I'm on the market for a sleeping bag and it's my first sleeping bag ever. I've seen multiple threads suggesting a quilt but I'm not sure if it's for me. I'm typically a back sleeper and don't wiggle around during sleep. My main use cases are camping and backpacking across West Coast(California, Utah, Arizona). I'm planning to backpack thru hikes about 40-50miles. I'll be investing in a good sleeping pad of R-value 4.5.

I've narrowed my options to two:
Western Mountaineering Ultralite 20F - (1 lb 13 oz) - Comfortable to 20F - Price $452
Big Agnes Greystone 20F - (2 lb 4 oz) - Although rated 20(I believe it's comfortable to 28F) - Price $208

Big Agnes is 600 fill DownTrek and WM is 850 Power Goose Down.
I'm really concerned if the 244$ difference in price is worth spending for my use case(for the 7oz difference and a 10F difference). I've checked the year round temperatures for the places I'd be visiting in Yosemite, Sequoia, Joshua and couple other places, the lowest I could see is 25F(across the whole year). Can't I get away with a BA sleeping bag for my use case? Somehow the 452$ price tag is holding me back from making the purchase, never spent so much on a camping gear before. Please feel free to suggest any other alternatives(must: weight needs to be around 2lbs and rated for 20F)

For context: I’m in my 20s and athletic(5 8”, 168lbs), so wouldn’t really mind carrying extra weight a bit.