Patti posted a comment to my Basic Ribbed sock pattern, and asked an important question.
She mentioned she'd didn't like the fabric she'd produced working with standard sock yarn on US size 3 needles. She said it was too loose and not stretchy.
Your yarn choice is good, it's actually the needles I'd change. Try much smaller needles -- 2.5mm (no US size equivalent), 2.25mm (US size 1) or even 2mm (US size 0).
She mentions that WoolEase sportweight works well on US size 3 -- yes, absolutely, it's heavier than standard sock yarn. Paton's Kroy is a terrific choice -- try it again, but use smaller needles.
You need to go small with sock needles, because you need a good, dense fabric that will stretch and bounce back, and will wear well. I always err on the smaller side of the recommended needles for a sock yarn, and for a yarn that's not specifically designed for socks -- the WoolEase being a good example -- I go down a couple from even the smallest recommended.