Isolation Feet Recommendation for Equipment Rack

I use steel spikes under my two racks into a 12" thick, 3000 psi steel reinforced concrete slab.   Nothing from the ground goes up into my racks.   However, the racks are welded steel with 50/50 mix of sand/shot.  They are relatively damped before getting to the shelves.  Most of my shelves are HDF 1 1/8" and others are 1" granite.   Then a mix of ultra and mini Stillpoints, one Audio Technica footer set and a Townshend Seismic Sink (turntable).  Some components are not footed (COS Engineering D1 DAC has excellent designed spikes/very solid cse and VPI 19-4 which has rubber & springs).   

I have just ordered 3 Giai feet to try under the turntable. Stunning that some of the isolation units for speakers cost more than some speakers I've owned. I'm sure the law of diminishing returns applies to these.

Sorry if I wasn't clear, it sure seems you got the wrong message. There is no such thing as diminishing returns, not if you do it right. If you compare for example going from dirt cheap Nobsound to Gaia then yes totally diminishing returns. You pay a small fortune for only slightly better, if that. Mostly what you get is convenience and appearance. Performance is a wash.

Going from Gaia to Townshend, now you pay a lot more but you also get a lot more. So no diminishing returns there. Actually the last time I heard this was moving Pendragon XL to Podiums, it was like a whole system upgrade. Brandon was saying it was like the whole room was treated.

That is why I abhor the diminishing returns canard, it is simply not there other than in the imagination. In reality you are as likely to find accelerating returns. If for example you had some expensive cones or spikes that cost more than $30/set of four then going to Nobsound will be better for less. So it can go both ways making diminishing returns more something comforting to say than anything connected with reality.

You can find out real easy, simply order a set of Nobsound and compare. It will take a bit of effort, they work a lot better after a little trial and error to get the number of springs just right for the load. Once you do that though I think you will find they come real close for a lot less. Then if you do Pods, they are not just a little better than Nobsound, but a lot.

Podiums are a big chunk of the cost of my Moabs. But they elevate them to Ulf level performance. So it is all question of adjusting to the fact the components themselves are not what it's all about, but what you put the component on is equally as important. 

Locking wheels are convenient.

OP: I just bought a 4-tier equipment rack to set up a 2nd system. It’s not audiophile standard and comes with standard spikes. Products are designed to perform at a certain level, period. Not convinced that adding something not originally part of the design will necessarily improve that product. Mounting Pirelli tires on a Yugo will not make it handle and brake like a Ferrari. Those characteristics would be supported by other parameters. Of course I could be wrong. I would have started with a better product in the beginning. Apologies for not helping so much.