LOL, you guys really crack me up.
The XR is a great bike, and i really like it. However the XR from 35km/h in top gear will take forever to get to 250km/h, as it has no torque under 4.5k, once the XR gets to about 100Km/h it will start pulling. The Superduke will also not go from 35km/h as it will shake your balls apart, and remember that the 5th gear on the SD is the same ratio as the S1000XR, the SD's 6th will do 300km/h in 6th.
The only bikes that can do the 35km/h to top speed in 6th gear, is the K1300's, Hyabusa's and 1400's, K1600, there is not replacement for displacement.
The XR vs GS argument. If you do not launch the XR from 4500RPM the GS will actually pull ahead for a while because of the torque. Have seen this and also did it.
XR on gravel is a no go. The XR's radiators burst when riding on tar never mind gravel. If they make a S1200(in line 4)GS and I will sell my GS for that bike.
Guys lets not forget one thing here. The GS and Adventure bikes are far more capable than you think, just ask Quinn Cody and Chris Birch whom both did the Redbull romaniacs with these bikes.