Try Argenmove, at Suipacha 612, 3rd floor. Telephone 4325- 4364, e-mail is "firstname.lastname@example.org"
They move the U.S. State Department, and they also moved me down. I was happy as a clam using them.
They can advise you on using lift vans, which are small containers that fit into a 20' container, and they are also excellent at navigating the Argentine bureaucracy.
If you call, be sure to ask for either Daniel or Noelia Ovieda, the owners (both of whom speak perfect English).