While your room isn't small, my Revel Studio 2's sound much larger in my 17x21x10 room than they did in my old one which was 14x18x9. If the Vandy has a restriction in height I can see the vertical stage getting bigger, but I'm not really sure a speaker change is warranted solely because you desire a bigger soundstage. If you have a 10' ceiling or more, perhaps so.
I see this similar to Tli. The Sasha II would likely work just as well in your room as the Alexia. Still, the only way to know is to hear the speaker in your room with your stuff. Which is awfully nice! I can see the dealers point of view on a home addition. Delivery and set up on the chance you might buy is a material risk/cost to a dealer. Still, you ought to be able to get the dealer to give you a home addition of the Sasha II for a fee. I'm sure they must have a pair on the floor, is $500, credited toward a purchase, for a weekend audition worth it to you? It would be to me.
If you can come to terms for a demo of the Sasha II you could also try this. Tell the dealer, in advance, that if you decide to buy the Sasha II you'd also like to hear the Alexia. Tell them you'll pay for the Sasha II upfront. They then give you a demo of the Alexia. If you decide to get the Alexia, you pay the difference. If they have floor demo pairs I suspect they'd do it.
If the Wilson dealer won't play ball, perhaps the Magico dealer would. Finally, the Vandy 7's?