@kennyc Your Audionet Humboldt is an integrated amp, right? Offhand, I would say a HRS R3X platform will serve you well.
I cannot give an honest A/B assessment of how the R3X and M3X2 compare. I started with a 19" x 17" R3X for a Clearaudio Innovation Wood turntable. That was about 65 lbs, and I had it sitting on top of a Naim Fraim rack. That worked really quite well. HRS factory tuned the R3X for that specific turntable.
Last year I upgraded to a Clearaudio Master Innovation turntable. That’s 145 lbs, and I did not want it sitting atop a Naim Fraim rack. I bought a HRS EXR rack to replace it. At the same time I also got a 21" x 19" M3X2 factory-tuned for the Master Innovation. I traded in my 19" x 17" R3X for a 21" x 19" version, and I use that for my Boulder 1108 phono-stage (38 lbs) sitting on the HRS EXR rack..
I never tried both R3X and M3X2 isolation bases with the same turntable before or after. The M3X2 works beautifully with the Master Innovation, but at 145 lbs I didn’t want to spare expense on isolation for it, especially in my 2nd floor room of a 98 year old house with springy wood floors.
The R3X is a fine isolation base and I think that will likely serve you well for a electronic component. I really only went up to the M3X2 because I wanted something better for a turntable.