Does your monitor on the left ever rattle from music?
Just that slight amount of difference in height would drive me up a wall. You both have nice setups though!
That desk speaker is technically 50 hz and higher. I have not seen the monitor ever move. I try to keep levels low at close proximity. I also use Bose noise cancelling headphones most of the day. The left monitor height diff did annoy me at first. I adjusted the Win 7 monitor position setting to account for it, as well as the Everest background that spans the three monitors.