Yeti, I find, with my foot shape, I have to buy one size up for SmartWool brand. I experienced the same discomfort, with the larger size they still stay in place but are not so constricting across the instep.

Sportsman's Guide has wool deals as well, and I just picked up a nice wool vest at Ross Dress for Less, you have to really dig for it in those stores. Don't know if you have them in your neck o'woods.