het part 2

By all means cover your McIntosh but not with a mcintosh.

Can you feel any heat on the top of the metal cases for either units when they are in "standby"? If you can't, I would say the recommendation of silk would be much more desirable than plastic vinyl. There will be a very slight amount of heat that could be detected with an infrared thermometer.

Get a light  cotton cover and dust with a Swifter only.

Cotton, too much lint in my opinion.
BTW my only piece of equipment that has a "standby", does put out a little heat when in standby. Nothing compared to an amp running at very low volumes though. I believe the heat rise from unplugged compared to standby was only 2-3 degrees.