Some clarifications:
The 030-50 is running at 50 MHz bus/ 50 MHz core clock.
The 040-25 is running a 25 MHz bus/ 50 MHz core clock speed.
So it's faster, but not several times, you must not compare the 040-025 to the 030-25 but with 030-50.
What kind of GOLF and Porsche are you talking about? The GOLF R32 is for shure not less advanced than the Porsche Boxter. GOLF is even more because it has exhaust gas temperature regulation, 4 Motion and the newly developped double clutch 6 shift automatic gear box. But the Porsche is a sportscar, the GOLF is a general purpose allround car.
And the Cayenne/Touareg are even developped cooperatively by VW and Porsche as are the Corrado, 924, 914 and all the old VWs.