Zlin,
Your tax has nothing to do with the countries in which the agencies reside, only the country in which you reside. Your salary is paid net of ANY tax, therefore it is up to you to fill out the relevant tax paperwork for your country of residence and pay that tax. Crew will deal with certain aspects of tax for the residents of the US but any non-US residents will have to file their tax returns with their own country and the agencies do NOT get involved in any aspects of taxation.
Yeah, the only agencies worth using are Crew and Parc..........use Crew!