I got the stepper dampers, and wow, night and day difference. Without a doubt the best thing since sliced bread. they isolate the steppers from the aluminum extrusion extremely well. According to my uncalibrated phone mic, they brought the noise down from 61dB to 48dB. Not a proper scientific study, but fun to play with.
I brought the stepper current back down to 800mA, I didn't notice any noise difference between that and 1200mA with the dampers.
I also got some sorbothane feet to reduce mechanical vibration transferring to my shelf and walls. Way better than felt feet. My next hurdle are the freaking jet engines I have for fans lol.