I would advise away from the Ashby heads, only for the reason of cost, as mentioned earlier. If you are just starting out, any of the other broadheads you've mentioned will kill anything on this continent with authority.
If you are just starting out, you may find it easier to sharpen a straight edge broadhead i.e Zwickey Delta, Magnus I, STOS, Magnus Stinger etc.
Learn to tune your bow and tune your arrows to your bow, keenly sharpen the heads you decide on and jump in with both feet! Ask lots of questions, this is an excellent forum for that.
Good hunting!
Kris