The question becomes how much power do you need to move your @@s around?? The 1200 is the breaking point between very good gas milage and more then enough power for 2 up to go anywhere.
At one time the 750 was the King of the road bikes for touring 2 up. The cops still use the 1000 and 1200 series around here. More portable in tight areas, comfort for tall riders and good gas milage for stop and go.
As far as speed goes a T120 Triumph will go faster then anyone I know will take it on a street or highway.