As to the K40, I read way too many reports on how the Bel and the Passport 8500 were far superior to the K40...it appears the K40 costs more, and they rely on this to make people think it is better.

If you really want to speed, the mounting of a Passport or Bell just below the rear view mirror is easier to suffer through than the invisibility of the K40, linked to speeding tickets :-)
Add the M40 laser diffuser, and the only thing left to worry about are airplanes or Vascar... I am still looking for solutions on these..