Tones,
Rather late in the day I know, but if you can't hear any difference yourself, then what is the point in this experiment?
If you can't hear any difference then is there really any point in acting on any findings of others to the contrary by (possibly) changing any of your equipment so that you may hear a difference yourself?
I can see why a Mana Soundframe, for example, would not have made a difference in your system given the furniture it was cited upon in turn and the effect this would have had in negating its potential benefits.
Your own scepticism regarding such tweaks as a Demag disc, cabling, supports or even a lobster sperm pen will only be overturned by a succesful demonstration to which your own ears/brain will be privy to.
In the meantime, it would be better to focus on making improvements that you can actually hear yourself that, in turn, will make your music more enjoyable to listen to.
Even if certain tweaks can be proven objectively to work either by "scientific measurements" or by any general consensus generated by this rather protracted experiment, if you still can't hear the differences for yourself then the whole operation of involving others and their own findings in this matter is utterly pointless.
Indeed, the opinions of others in this regard should be considered as irrelevant until you are able to hear genuine improvements in musical reproduction for yourself.