Amphion Argon 3 or Lenehanaudio ML1

The Argons are excellent speakers. I'd be concerned about putting them inside an armoire, they are not small, and they put out a surprising amount of bass. Maybe look at their little brothers the Helium.

If you are planning on keeping the speakers in the armior I think a front ported speaker like the Trianle Titus ES or Triangle Titus Titus XS might both be all the speaker you will ever need for great sound in that space.
They are also very efficient, so may pair up better with your 55 watt amp.
The XS can be found here for around $250, and the bigger Titus ES for around $350. I would try one of these speakers first. You may be blown away with the sound of the Traingles and see no need to spend more. If not, you can re-sell them for no real loss.
I have had only 2 sets of rear ported speakers. ( Sp Tech Minis and Green Mountain Europas ) Both speakers needed at least 24 inches from the wall to sound their best.
I really think both the Triangle ES or XS might sound better than the Amphion or Lenehan Audio speakers in that given space.
There are many options for front ported or sealed moitors that are efficient for under $600.
ATC also has sealed monitors for about a grand that may work really well.
Guru speakers are also designed to be against a wall.
Todd

Matt

Depending where you live I can put you in touch with someone who will give you an in home demo of the ML1's. Can't figure out how to email you on Agon.

Matt don't you have room for speaker stands?

What about Lenehanaudio ML2 instead of the ML1?

Both of these speakers are reported to be great monitors.
If I was going to put my speakers in an armoir I would want a front ported speaker or sealed monitors. The last thing you want is boomy muddy base ruining the sound of these great speakers.

I guess the armoire is flat against a wall. My opinion is that you should not spend this kind of money when the positioning won't let either speaker sound their best, unless it is temporary. Both are great stand mounts at their price points.