My D-handle base came as part of a router package I bought from Amazon.com.  I can't imagine not having the D-handle.  The toggle switch on the PC 690 is not very conveniently located.  The D-handle base has the  trigger switch, which turns on and off without fumbling or taking your eyes  off the work.  In addition, I think it gives me a more stable grip than  holding the two standard knobs on the sides.  Forward-backward tilt is much  more easily controlled with the D-handle.