The name "Goupe Sechs" is German for "Group Sex" as the name sounds like this when being said. It is also a pun of the infamous European security company Group 4. In GTA IV, the written logo is changed to "Gruppe 6" which still translates to "Gruppe Sechs" in German.
In GTA Vice City and GTA Vice City Stories, the location of the company in the city is unknown. The company's cars can be seen driving around in Viceport. In the PC version of GTA Vice City, a Securicar can be found parked in front of the El Banco Corrupto Grande.