Isolation Feet Recommendation for Equipment Rack

I just bought a 4-tier equipment rack to set up a 2nd system. It’s not audiophile standard and comes with standard spikes. The sound quality of the system is decent with this rack but I intend to replace the spikes on the rack with something else in the near future and was wondering about the available options.

The target support weight inclusive of the rack is up to 150 lbs (on a more accurate level it's around 130lbs). Apart from the Isoacoustics Gaia, are there any other worthy options around the same price range? What about the Finite Elemente stuff such as Cerabase and Cerapuc? I have the FE Cerapuc installed on the equipment rack in the main system but did not compare the Cerapuc with anything else for the past 15 years of ownership.

I would appreciate experiences from folks who have switched from spikes to any of the "audiophile standard" isolator options on the equipment rack, going from coupling to decoupling. These isolation feet will need to bring some noticeable if not significant change or improvement to the sound quality of the system after they replaced the spikes on the equipment rack. If the difference is subtle to the point of negligible, or the sound becomes worse instead of better, I’d say forget it.
I have brass cones and granite on the bottom shelf and 2 inch thick maple shelf’s ,I use Stillpoints  which are excellent under 
my gear.

  "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" 

Simply not correct.  Critical Mass Systems footers are so much ahead of all other isolation devices (I've tried everything) you should think of them as component that context they are great value. 

One more point: any kind of rubber is bad (including the long fibre jobs like sorbothane) anywhere in your support system. Forget all that BS about rubber converting vibration to heat.  Rubber does not absorb, but simply returns a large portion of the bad vibes after a slight delay. This is far more apparent as you move up the sound quality gradient. 

Best wishes
Your answer is easy try the Pneuance Audio Pneupods. They will work with your weight and can screw right in to your existing stand. They are wonderful isolators check out their findings beat many contenders. 
Do you have a turntable? If not don't bother. Buy some music instead. 
Even if it sounds better initially that will go away as you get use to seeing them. Isolation in important for turntables only. Generalizing it to other equipment is just a ploy to make money. Remember, if it looks good it will sound better.....for a while.