There is a Viatnamese restaurant in Palermo. It is very expensive as well. They are called Vietnam and are on Gurruchaga 1776. There is a little gift shop out in front.
Have you heard of guiaoleo.com.ar? It is a great user rated index with all the listings of restaurants in the city. You can search by barrio, price, type of cuisine, wifi, and basically any parameter. I would be weary of the comments sometimes because as an example the review for my favorite korean place (Bi Won-Junin 548) has a review that 'The food was too spicy, and the lomo was not so great'