So, today I received a couple of Monk Plus earbuds (Smoke, and Coffee Gold w/3-Click Mic), and now I know why people on here kept saying that the Monk Plus doesn't have very much low Bass performance. Before today, I've been listening to my Espresso Edition 2.5TRRS Monk Plus, and they have much better low Bass impact than these standard versions.
Also in the mail today, were the Qian25 and Qian39 earbuds that I ordered. Comparing them to the various Monk Plus earbuds (all with Hiegi donut foams), and connected to my Shanling M1 (playing Amber Rubarth's "Sessions from the 17th Ward"), my impressions are -
The Qian39 and Coffee Gold Monk Plus sound similar (NOTE: due to different impedance, I had to try to volume match), with the Qian39 having a slightly more forward Midrange, which provides a bit of additional clarity. Both of them have less Bass impact than the Qian25, or the Espresso Edition Monk Plus (connected with a 3.5TRS to 2.5TRRS adapter).
Because the Qian25 has more Bass, it's Midrange seems to be slightly recessed (especially compared to the Qian39), but it's still as clear as the Monk Plus models.