Hello hot knife,
I have had a pair of 18s since the day they arrived at the Greek dealer and I was super happy with them. They have very clear highs and a good capability in lows. After two years I added a beolab 2. Big improvement to the whole setup. I have the 18s and 2 connected to a beoplay v1 and I am using the setup for movies and music (almost any kind of music). According to my humble opinion they sound better when the signal processing is done by the V1 rather than a third party amp or tv. The reason I believe is simply that the V1 is doing all the sound processing and by that I mean that V1 (or any other B&O TV) "knows" the speakers you have connected to it and can do stuff like bass redirection etc.
In November 2018 I bought a pair of 9s to use with my beosound moment strictly for music listening. I knew from the begging that the 9s were (and still are to my opinion and wallet caliber) the most reasonable priced high end speakers made by B&O. They have a superior imaging (at least this is what I noticed) in comparison to the combination of 18s and 2. Furthermore they sound fantastic in all three bands (highs, lows,mids). I have tried to connect the 2 to them only to realize that at least for music the 2 is not needed. The combination of Class AB amps for mids and highs and class d for lows is magical for music listening at least for my ears and sound taste.
I definitely recommend the 9s but this does not mean that a pair of 18s do not sound good. I also had the opportunity to spend some time with a 18s and 19 setup and I have to admit that it sounds far better than the 18s and 2 setup even when they were playing from third party amp.
All in all my preference is
9s
18s+19
18s+2 (only when you have them connected to B&O equipment)