I used to own Sonus Faber Olympica 3 and now own Sonus Faber Amati Traditional I just recently helped friend outfit and tune his 9’ by 12’ audio room with Wilson Watt Puppies.
You would be very safe with Olympic 3. They are not huge speakers and if we assume you are going to have a 6’ triangle and place the speakers along the narrow wall (after a year of experimentation that is where we ended up with my friends system) then you have 2.5’ on either side and easily three feet behind... or more. They will sound great with that.
One of the great things about Sonus Faber is you can put the speakers really close and pointed right at your a they never get harsh. That is not true with many speakers, They are really flexible in spaces.
We have treated my friends room... you can turn that system really loud and rock out and it sounds simply fantastic.. I really don’t think you should have any hesitation on Olympica Nova 3. I would imagine that with treatment used at moderate volumes Serefino will sound even better. I guess if it was my money I would get the Serefino.
I just went through a slow and methodical movement of my speakers from close to the wall. I have a very large room, so this is not completely applicable to your room. I was surprised, they sounded good a foot or two from the wall, not something I would not be happy with But the best is out about five feet. But it isn’t like night and day... they really sounded great everywhere. If closer, they need more dampening behind to get a really deep soundstage.