High end speakers at low volume

@jackjohnson316 thanks I’ll check the Buchardt. Problem with Zu is that there’s no dealer in Europe and I should buy them without listening. Also I didn’t understand if working well with classic rock music.

@pscar glad to hear your feedback. First one to consider Sabrina X good at low volume perhaps !

@ricco275  

Pros:

- Point source (soundstage/imaging)

- Coherency. You're not forcing multiple drivers to work with eachother

- No Crossover. Crossovers smear the sound, so you lose a noticeable amount of detail in the crossover region. It's not something you can measure with certainty on a graph. It usually shows up as a slight dip.

- Clear midrange/treble

- Bass speed (if transmission line is used)

- Efficiency

Cons:

- Stigma. The "science people" are convinced that single driver speakers are inferior. Because dogma.

- Not as loud as 2 or 3 way speakers. You typically use single drivers at moderate/low volumes. There's definitely an ideal volume for this design, and it's not party music loud. 

- Beaming of high frequencies at loud volumes. A phase plug helps with that. Better drivers help with that. 

- Most single driver speakers with cheap drivers have uneven frequency response with for example no bass and/or shouty midrange. So at the budget level you're better off using cheap drivers and a crossover. Some single driver speakers have filters to fix this issue. Good fullrange drivers are few and far between. EMS and Cube Audio are good examples. And speaker designers love to tune the sound with transmission line cabinets. 

- It's harder to get room filling bass with a single driver. You can go with a larger driver (21cm) with a whizzer cone. But you'll compromise on treble and imaging. You can go with a smaller driver (4 inch) and get amazing midrange/treble/imaging at the expense of bass. Again, some unconventional speaker designers achieve bass with small drivers through specially tuned "active" cabinets which resonate like a musical instrument. Or use a sub. 

- Resale value suffers because of the stigma. It's not like you're buying a Sonus Faber, Wilson Audio or Focal speaker which flies off of the shelves. 

I will say that the OGY works beautifully with Classic Rock, Blues and Jazz. Because guitars and vocals sound so natural. You'll just want more rumble with heavy metal music (a sub helps a lot with that, but you might enjoy a Buchardt S400 more without the sub). 

If you're in Europe, then the best speaker I heard for the money is the Audax AM21 assembled speaker from La Maison du Haut Parleur. They do it all! I just got the OGY instead because I have a smaller room. 

I think one of the biggest limiting factors for you is how close the speakers have to be to the wall, 25cm is not far. Most speakers. Need a meter or so to breathe properly and make good bass. I see the Vandersteen treo is on your list. I'd recommend you try and find a used or demo pair of quatros. They have a subwoofer built in with a bass management system that you can tune to your room. This means you can get the speakers really close to the wall and still achieve good bass which is often what is missing in lower volume listening. I have a pair and I listen around 65db most of the time. They image incredibly well, are true to the music, and my wife likes the way they look. Check em out. 

Klipsch Heratige, Forte, Cornwall or LaScala depending on your room, could even look at Khorn. I have Fote III and a low 10 watt SET KT88 Inspire amp, plenty of detail, spooky good stereo sound stage and dynamics at low volume.