With 20 subwoofers in a 14 by 11 listening space. I have always found that it does not make much difference , worrying about hard drives, seeing as if I cant keep hanging pictures on any walls without getting unwanted vibration noise, and seeing as, the vibration on my wall mounted shelving is probably close to being right on top of some subwoofers, I doubt you will have many issues.
You may wish to keep a complete extra hard drive , cloned in case.
I have had over 15 drives subjected to a lot of vibration, and never had any performance issues with the drives. This is with all those drives in desktops on a shelf directly above 6 ported 15 inch subs. and the rest of the subs designated in left and right channel positions.
It would not hurt to try and dampen them off as you are doing. All the best!
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A Good amplifier requires a adequate power supply, It does not matter what the amplifier is capable of if the power supply will not provide the power required. Most amplifiers have under rated power supplies. It is up to you to make sure you get the ones that are least under rated if at all.