I know this is an old topic, but I'd like to give my $0.02
I started out using a rock, I continued using a rock and was still able to make some pretty objects, along with the staples (hooks, nails, etc).
Then I was using a russian cast steel ASO, I was able to make some better art work, but I still needed the skill to back it up.
Now I have a Peter Wright, it is an excellent anvil and I move metal much faster, but it still requires skill, much of which I still need to learn.
A Peddinghaus/Refflinghaus would be like the Rolls Royce of anvils (Kohlswas are Mercedes'), and metal would move very easily, forging would be like butter, but you can't make better shapes on those than you can on my russian ASO if you have the skill. That's my Two Cents