Vandersteen Treo CT vs Mag 3.7i speakers

IMHO, both are great choices, and ultimately it will just come down to personal preference.

How far out from the front wall can you place the Maggies?  I have the 3.7i's, and my brother owns the Treos (non CT).  If you can't get the Maggies at least 5 feet from the front wall, I'd go with the Vandersteens. Also, what type of music do you listen to? The Maggies are not ideal for rock. Integrating subs is also very difficult.

Rock was one of the reasons I got rid of the Maggies quickly years ago.  I hear them a lot at friends houses etc... and I still like a lot of rock also.  Vocals they are cool, but yea, the Vandersteen's really are versatile

Limniscate -
I can place the Mag 3.7i about 4 ft from the front wall.  

newton, though 5ft. or more is optimum for planars (all, not just Maggies), 4ft. can be acceptable if you treat the wall behind the speakers with either absorption or diffusion. Absorption for a smaller, more "direct" sound, diffusion for a bigger, more expansive one.