However, I thought the Soundfield Audio's top feature was it's deep extension and efficiency
Not at all - its top feature is the KEF-sourced 5" aluminum coaxial driver plus tangerine tweeter guide covering 200hz on up. With the 8" woofer taking away the need for it to produce lower frequencies, it's the mids that benefit with top class resolution and accuracy.
Unlike every since speaker on that list of yours, this one will actually have an even sound power response into the small room, which will give a more natural tonal balance. The rest are all just basic box speakers with a power response dip in the midrange accompanied by a power response peak, as the large mid transitions to the small tweeter.
For example the Ascend sierra one at 45 degrees off axis:
See how there's an increase in treble response after 1.5khz or so? That's why I wouldn't want the sierra one - the sound reflected by the room is not balanced.
The Soundfield M1 even at 60 degrees off axis:
Shows pretty much none of this behaviour in the upper mids/lower treble (a bit more energy in the upper treble, but these are benign frequencies, which are more readily absorbed by rooms anyways). The off-axis response declines smoothly. The speakers on your list will not have this important feature.
Also being a coaxial, the vertical, horizontal sweet spots are significantly wider, whether that matters or not, it's never a bad thing. With the recommended cross-firing you will get a very nice soundstage.
I mean, yes the woofer can dig pretty deep, and that's cool, but it's an interchangable part. The coaxial mid/tweeter is not - it's the star of the show. The Q100 however forces it (the same driver) to play too low in frequency for best results.