I know it's not in the southern area but I vote Breckenridge. It's massive and has something for everyone, including some of the best terrain parks in CO.
It also has some amazing places to eat, great shops, and great nightlife. It's actually a town, not just a resort "area".
Plus Keystone is right there too so you can go night skiiing. If you're up to it, you can pretty much double up the amount of riding you do on your vacation.