Firstly the monster Sigma Genesis was designed by the founder of Zyx - so if you like the sound of your Monster have a look at the Zyx range as an alternative to the Hand Umami.
I have owned an ET2 for over 30 years. You do not need the Magnesium arm to run a low compliance cartridge - it is not essential, though it might improve the sound. All you need to so is use the correct leaf spring and weight combo for low compliance cartridges - less counterweight further out on the beam.
Personally I don't use any dampening trough, I find it slugs the sound.