This one is for you, Timo
In TNG I stumbled upon this little gem from "Face of the Enemy":
DESEVE: The freighter is an old Antares class vessel with limited speed and range. It couldn't have taken on its cargo more than a day ago which means it must be within fifteen light years of here.
That comes out to about at 5,457c or 15 LY per day.
That would finally give TNG a speed faster than the stated ones.