It is surely a good advise. But my question on the BLUE BOARD is it all the agencies who pass thru Proz.com.
Have a look at the Blue Board FAQ:
What is the Blue Board?
We'll explain in a roundabout way. First of all, any ProZ.com member can enter a number from 1 to 5 corresponding to his or her likelihood of working again with a given outsourcer (ie. client or translation company/agency). By way of explanation, the member can also enter a line of text along with the number. In response, the outsourcer may enter a line of text of his/her/its own.
The Blue Board is the complete, searchable database of the records containing these entries and replies, along with outsourcer coordinates.