The Soup Peddler's split pea soup is some of the best I've ever had. I know they go to the trouble of making a ham stock first, then using it as a base for the soup. You might look in a copy of their book for their recipe.
to be honest, i always use the recipe that is on the back of the bag of the split peas and increase by about 20% the amount of celery, carrots and add louisiana or crystal hot sauce and it turns out great