Colin,
Don't be too hesitant about converting horses. I was hesitant as well. It seems as a daunting task at first, but once you get started with it you will find that it is not so bad. Just get the rough musculature down, and then go back and refine it with smaller pieces of putty blended into the base you already created. Work in small areas and use good references and before you know it, you end up with something that resembles a horse. It is a satisfying exercise so try it out!
Thanks again everyone for your comments!