My experience has been that once you get to the level you like and can handle a liter bike, you don't like less.
But there's a lot of lee-way there. But while you can talk horsepower, torque is more related to displacement and you can't get the feel of a liter bike from a 650. Here's where I have laid down some experiences, granted this was several years ago and I have not updated it in years:
http://www.bikepics.com/members/kamerer/
Bike I bought for commuting and never though I'd love, but do? 1983 Honda CB1000C. Upright riding position, very retro-standard. Enough torque and weight to be stable, but not too much horsepower to tempt you into foolishness. But just enough to do whatever you want within reason. A great "mature rider" bike. Don't hesitate to look at older standards to meet the need I think you are going for.
But there's a lot of lee-way there. But while you can talk horsepower, torque is more related to displacement and you can't get the feel of a liter bike from a 650. Here's where I have laid down some experiences, granted this was several years ago and I have not updated it in years:
http://www.bikepics.com/members/kamerer/
Bike I bought for commuting and never though I'd love, but do? 1983 Honda CB1000C. Upright riding position, very retro-standard. Enough torque and weight to be stable, but not too much horsepower to tempt you into foolishness. But just enough to do whatever you want within reason. A great "mature rider" bike. Don't hesitate to look at older standards to meet the need I think you are going for.