Hi, ghunter. Iso-Cups work very well with most audio and video components. We have lots of customers using them with ss amps (including monos), CD players, preamps, conditioners.
With most components, Tenderfoot isolation feet and Iso-Cups will both deliver very appreciable sonic benefit, with neither being particularly "better" than the other, though personal taste might deliver a preference.
Tenderfeet will usually have an advantage over Iso-Cups with very lightweight components, though their use certainly isn't confined to light components.
Because tube amps have been used as the reference component for Iso-Cup formulation and development, Iso-Cups work particularly well with tube amps, but that does not preclude their use with other components.
Tenderfeet and Iso-Cups have been featured together with our product lineup for several years. Both have gone through several incremental formula improvements and have periodically teeter-tottered as to which is "better." All the while, neither has been able to "knock off" the other from the product lineup. They have both achieved quite a state of perfection.
I suggest giving Iso-Cups a try with your monos and try Tenderfeet for your other components. You can swap the footers around to audition amongst your components and use the combination that gives the most preferable result.
SteveHerbie's Audio Lab