I have no experience of active systems. But the idea of bypassing the crossover is appealing and, theoretically, should provide better results : revealing speakers!
If “revealing” is your thing, which I suppose it is, then you’ll surely enjoy the 500 DR with Magico S or M series. Magico speakers are extremely revealing speakers. The 500 DR and Magico blend perfectly.
So I wouldn’t go for passive unless being sure to have the right speakers.
As for adding a 555PS DR to the ND555, I wrote little review that could be of some interest.