KEF Reference 3

A friend of mine owns them less than half year. But also owns much more expensive gear and sells them to me to a very attractive price. Yes I'll try to hear them again.

Where did you hear them? Bring your Marantz the next time. 

Exactly. These are pretty accurate speakers and this sounded weird in my ears.

I am accustomed to the rich and little warm character of concepts but still with much detail and information and 3D soundstage.

But KEF's soundstage and depth was exceptional better than concepts like there were no speakers in the room and sound filled the room from all directions.

But the room was different to my home's space and the amplifier costs 2-3 times the Marantz. (Macintosh ma9000).

I have to hear them again for sure to reach to safe conclusions.

I own KEF Reference 3s so you should understand that I’m biased in their favor.  I am also not familiar w/ the Q acoustics Concepts. We are all guilty of promoting gear we own.  That cleared up: 

the KEFs are well regarding for imaging and soundstage - things you noticed.  Based on their white papers, this was a design goal of their coincident driver and a fully realized design goal.

I would also suggest the KEFs are quite accurate.  You noticed them as being very detailed and analytical.  Today, companies like KEF and B&W use their significant engineering prowess to make accurate speakers to most price points. They have resources that few other speaker manufacturers can match.  

It may very well be that you perceive the KEF as dry, but with proper setup and decent equipment (and I think your Marantz gear should suffice - though the speakers will clearly also reward moving upstream) the speakers were reflecting what they’re fed. 

Of course, some prefer the more romantic sound of Sonus Faber. Some prefer richer, brighter, darker, more dynamic etc.  The KEFs, for their price, are just pretty accurate. Perfect? Of course not.  But, I do find them really rewarding on most things.  On some poorly recording music, I’d benefit from a more forgiving presentation. But that’s really not the fault of the speaker.

So, it comes down to what you want.  There are others who believe there are much better options.  But really, it’s all a matter of taste - what do you want in a speaker?  For me, I no longer want for more from my speakers.  And, I’ve been through more than a few and listened to many, many options before purchasing.  

I would suggest you listen to them again - at length.  Perhaps you could even bring your gear.  It’s a big purchase.  It takes time listening to get comfortable with a decision either way.

Good luck and let us know what you decide.
Best, 

Thank you for the response.

Have you ever compared both speakers?

Do you also have any suggestions for other amp/source?

I thought the Marantz combo is good enough.

The Concepts are good enough to see you through upgrading your upstream components. I'd put my money there instead.