I actually have the K40 installed in my 98 GTS. It has both the front and rear detector, as well as the optional laser jammer/diffuser. The reviews on it are top notch as far as fighting laser, and it does work. The only problem I have with it is I have to turn it on after the car is running. The detector freaks out if it's in the on position when cranking the vehicle. It basically causes it to fail the self-diagnostics.
I know this thing works, as I've had those stationary radar displays on the side of the road read absolutely nothing, or _ _ as I drove by. I also picked up a cop over 1/2 mile away while driving at 2AM and managed to sneak by without raising suspicion. I'd say keep it as long as you have the optional laser jammer.