Vertical Stacking Equipment

It is better to have individual shelves in the rack/cabinet/closet: and then only the weight of each single component is on the properly sized isolator feet.

you can get strong tempered glass shelves made that are thinner than wood, 1/4" is very strong, they make 3/8" t, for a long span I had 1/2" thick made for the top of the riser I built for my TV so the center channel speaker fits below the image.

leave gaps and drill holes in the back (and/or shelves) as needed for ventilation, I cut big holes for access and ventilation, and made a removable back panel, so looking thru from the front it is dark, you do not see wires against a light colored wall

https://www.audiogon.com/systems/12369

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.