Well done - I have just done the same thing this week, 99 LS400 said a sad farewell as the new kid 05 LS430 moved in! Fantastic!
The 430 has Nav / ML audio, but I have to say that the audio - while good, is not as good as the LS400 (which had the Naka head end I think.) What is different you say - well the AM radio performance is a big dissapointment - while the signal reception ability is good the AM signal lacks the clarity and extended High Frequency performance that the 400 had. Yes I can hear you all out there - "AM Radio - what is that?" But AM frequency response does go out to 7.5kHz and compromising the IF stage peformance ruins the frequency response of the AM radio. (Hey stop laughing out there) The FM performance is fine.
The other thing is the oddity with the ML CD audio (which I also didnt like in the demo IS250 we were loaned before taking delivery of our new non-ML-equipped 06 IS250 [also a great car]) The LS400 had clearer CD audio, more open, better imaging and not such a "smeary" sound. Yes - the ML goes loud, has stacks of bass, etc, etc, but there is something else going on in there that is a step back from what was without a doubt the best factory audio that I have ever heard taht was standard in the 400.
All that aside the 430 is simply fantastic and I am so pleased that I did not buy that Benz S500.
The mornings are a hard choice - do I take the new IS350 or the LS430 (snigger)