Vertical Stacking Equipment

You can use "antivibration" pads that are made for going under your washer/dryer. Dense rubber and about 2" dia, they are very inexpensive. I've put them under each of my turntables. Got them at Amazon. They come in sets of 4.

I make my own out of wood. Same dimensions (1x2). Cut the length to spec for the components, then stain and glue some felt on top and bottom.

Hi rbschauman

I think there's nothing wrong with your initial approach of using the Nordost’s Sort Kones, as long as the Kones are capable of carrying the combined weight of the stack on top. E.g. in case your stacking all 4 components, the total weight will exceed 80 lbs, meaning the bottom ones need to support >80lbs, whereas the top one only 16-25lbs (depending what you put on top). I really like elliottbnewcombjr's suggestion to put glass shelving in between. Not sure whether that's possible in your cabinet though. If you think the Nordost Kones are too expensive, I used Stack Audio Auva isolators, those are very good: https://stackaudio.co.uk/product/auva-equipment-isolator/ Make sure you order the correct version depending on your weight requirements.

More affordable versions (not as sonically good as Auva's) would be the IsoAcoustics Iso-Puck Series Acoustic Isolators (Iso-Puck Mini, 6 lbs max/Unit, 8-Pack) https://www.amazon.com/dp/B07V25PWQL?th=1 These come in different weight classes.

Good luck!

@rjvissers +1  Yes, proper equipment stands are best, but you knew that already.  You are looking for less capital involvement.  Herbie's are also quite good.  Cumulative weight will be an issue risking cabinet deformation.  Good hunting.

You can space them apart, stacked, by using four  sorbothane pucks between them - try and avoid placing them to cover any ventilation slots.