Wilson Alexia - speaker placement question

Chances are at two feet out it might work well. Most speakers that need a little space work in the 2 to 3 feet range. Planers might need more space but that is not your issue. 

Going by the room dimension the width looks good and the ratios are not bad -

2.3 : 1.8 : 1 (2 : 1.5 : 1 evenly spaced room modes).

You have some distance from the side wall to work with.

Pick up 4 - 6 freestanding absorber panels to start - this should give you a good place to start.

Is the 20-30 inch limit going to the front of the speaker?

Also Wilson allows for some adjustment of the ports ...

"I can only keep the speakers 20-23 inches from the front wall."

$50K speakers and you can't put them in an optimized position. 

You probably  will get them to sound good in any location, but a speaker especially like  that deserves to at least be influenced by the "rule of 1/3rds" -7ft or Cardas type distances from the front wall.

http://www.cardas.com/room_setup_calculators.php

From TAS review

"They worked beautifully when placed well away from the sidewalls and near the rear walls in my listening room. They have a surprisingly flat response down to around 34–37Hz, going much deeper with a slow roll-off, with audible and measured power to below 30Hz."

I have Alexia 2s in a NYC apartment which has your exact dimensions 16x21x9.

My speakers are 19" from the front wall at the rear inside corner of the toed in cabinet. The speakers fire down the long walls to my seat. The walls are dense plaster. I could move the speakers to  within 18" for more bass reinforcement and that would work too, but once I move to 20", I lose too much bass reinforcement and gain nothing. That does not mean this positioning will work for you but it worked within an inch for my previous Sashas and WP 7s in my room. Good luck.