OP - I'm not so sure I'd agree with the posts that reckon that you'll be disappointed in moving from an e39 to an e60 (or that they are a money pit). I have both at the moment. I love e39's but the e60 is a fine car. It does pretty much everything that the e39 does. It probably does lack the last n-th degree of driver involvement that the e39 has but you could say the same about the difference between any two generations of BMW over the past 25 years. e30 more involving than e36, e36 more involving than e46, and so on along the line. While I wouldn't necessarily have the same degree of love for the e60 as the e39, I wouldn't say its disappointing in any way. Its a car of its time - and as capable as any 5 series.

If you aim for the earlier (pre N47 engine) you MIGHT just feel a little bit underwhelmed with the grunt compared to the 530d, and it won't be a straight 6, but in the real world it mightn't matter too much. Obviously, its the price to pay to avoid the potential for a timing chain issue on an N47.