Vandersteen 5A or Sonus Faber Stradivari Homage

Prolly should go with the Vandersteens, I have heard them and thought quite differently than Zd542 in that they were on the warmer richer side of the scale. They are fantastic with analog if you have a turntable.
That said you already favor the Sonus Faber "house sound" so you should listen to the bigger ones you want and see if they retain the sound you like so much. It's your set up so go with what really pleases you. Sorry for stating the obvious.

If you are looking for something that sounds warm/forgiving, the SF will probably be a better choice. The Vandersteen uses an aluminium tweeter and is a more detailed speaker overall. That said, the 5A has a lot going for it in other areas. It may be a safer choice. The Vandersteens are very transparent speakers in that you can do a lot to change the sound of them. They're very revealing of the components upstream. For example, if you find them too bright, you can get different electronics to completely change the way the system sounds. I know people will say that changing electronics will alter the sound of just about any speaker. I agree, but the point I'm trying to make is that with the Vandersteens, its a much bigger change. Either way, you're still going to have to listen to both pairs of speakers before you make a choice.

I have not heard the Stradivari's , but was at a dealer the other day and he had the Carbon 5A's playing. Although not fully broke in, I was really impressed with what they were doing. He has the 7's set up in his main room with D'Agostino front end and I have heard these many times. As much as I love what the 7's do, I felt the 5"'s we're performing on the heels of the 7's. The 5's were in an ARC front end using an LS27, and sorry I don't recall which mono locks. But I really thought, if I could, I would be hard pressed to spend the extra for the 7's based on what the 5's (not yet fully broke in) we're bringing to my ears. I guess in short, the 5's present a tremendous value in the price range and nip at the heels of speakers costing 20-25K more.
Just my opinion of course.