The top of the line in K-bikes, from my point of view:
K1100LT Special Edition
My first BMW was a K75C model. This three cylinder in line bike was a true pleasure to ride. The engine is very smooth and the Plexiglas windscreen makes driving at high speeds very comfortable. What the bike missed was the full fearing providing more protection.
After 2 years I moved up to the K75RT (1992) with ABS brakes. These bikes are hard to find with the ABS brakes. Once you have had to rely on the ABS during an emergency stop on a wet road, this feature is a must on all future bikes. At least in my opinion. The electric window as a great option. Up to 80-90 km/hr the window in raised position will take most of the wind away. With higher speeds I find it more comfortable to lower the window and thereby also reducing the drag of the bike.