I've wintersown echinacea several times, with pretty good results. Not all seeds germinated, but enough to satisfy me. And those that did sprout grew into nice healthy plants.
Chelle, Prarie Sun is my all time favorite rud hirta, too. After many years of saving my own seeds though, they had crossed pollinated with others and didn't look much like the original anymore. I bought a fresh pack of commercial seeds this year and wintersowed them.
Karen