With all three monitors, and the second screen for the right system, there just isn’t room for something that big as far as I can tell. The wall just isn’t that big .Another possibility would be to put the speakers on either far side of the monitors and toe them in steeply. With enough toe-in, it could sound surprisingly good. But you are not going to get good sound out of tiny speakers placed under your monitors. They will be so lacking in bass that they will not be able reproduce male vocals with any degree of fidelity, let alone things like kick drums, bass guitar, cello... it would be a very long list of things that would be faint, distorted, or missing entirely. Then the reflections from the desk willl ruin the midrange, and the off-axis position of the tweeters will mute the treble. I don't think you'd be happy at all.
You don't have to spend a lot - $200-300 for some quality bookshelf speakers with 5.25" or 6.5" woofers would sound amazing in a near-field arrangement.