Alternatives to Stillpoints

I am using the Stillpoints Ultra SS with good success in some of my gear. Looking to complete two more sets. Then it hit me, is there anything better (preferably cheaper) out there?
I received an order from Herbies a few days ago and my results are puzzling.
Bought 3 isocups and lamp black balls to place under my Ayre ax7e amp.

So placed under the chassis bypassing the existing 3 feet wrought a slight increase in depth and bass.

However placing under the existing feet gave a considerable change! Much improved bass and top end, almost like I had hit the loudness

I thought the idea was to bypass the manufacturer supplied feet and go direct to chassis.
Tbh I was truly surprised to be really hear anything this noticeable. And I swapped back and forth many times just to be sure at least in my mind.

Any thoughts?
I like Herbie's products across the board and use the iso cups and balls under my Primaluna mono blocks to great effect (on Himalayan salt block platforms).
Hey Andy,
Where did you get  Himalayan salt block platforms large enough for your mono blocks? 
Amazon. I think this is it:

It's 12 x x 8 x 2 so it's footprint is a bit smaller than the amps.