Shahinian Obelisk vs VandersteenTreo

Yes, Quatro's would be the way to go, in my opinion.
The upgrades between the 3a sigs and Treo/Quatro line is significant.
If you are looking at the ones for sale here on Agon, I am looking at them, too.
I really like the Shahinian's, but their design is mostly based on the Bose 'direct/reflection' theory. You get lots of nice diffuse sound, very relaxing, but lacking in structure and definition. A properly set up Vandy will give you a more precise soundstage. IMHO.
B

Gdnrbob,
Thanks, but... The Q now is: Treo at $4K or Quatro at $5200? ;-)
But, I guess, this is now up to me. 

I would contact Johnny Rutan and get his opinion (audioconnection).
Also, contact the sellers directly. You can get a better idea of what is being offered.
Bob

Sure, Bob, but calling a dealer in the US won’t help me much here in Russia :-)
The items are not on Audiogon. But I have spoken to the sellers, of course. Thinking...
Looks like Quatro is the way to go, since its bass performance can be tweaked. 

I Didn't know about your being in Russia. That makes things a bit more complicated. I never would have guessed it, as your English is impeccable.
You can certainly PM Johnny R and get great advice for free. He is one of the premier Vandersteen dealers in the US, and for good reason.
I would agree, getting a pair of Quatro's would be the best way to go, for the long run. You have a fairly large room. The Quatro's would be a good fit.
And, Johnny can help you with assessing your current amp and preamp, which, should you get the Quatro's, would probably be worthy of another upgrade in the future.
Bob