Judit, as we know, there are proper applications for different coin denominations. Obviously you are aware of this, and I was simply mentioning my use of the 25 cent application. However, I would never be "nouveau riche" enough to use 25 cent models, when 5 cent models will suffice. :^)
Edesilva has a good point(ha!) that some very heavy things could punch through the coins. That means that the frugal audiophile will have to resort to "punch outs" from steel electrical boxes, which are about the size of coins, but made from steel. Still cheap and effective.
I don't like to spend alot on certain simple tweaks, because then I can spend more on my new amps, or whatever.