No, I think the most important thing (your ears) are telling you all you need to know. But that doesn't mean if you don't obviously hear it that it isn't an improvement. Take vibration control, if you do it to one piece of equipment, you may not hear a difference, it depends on two things, the sensitivity of your equipment and the sensitivity of your ears.
Ric Schultz of High Fidelity, has some YT videos, one in which he suggests replacing the (magnetic, steel) screws that hold your speaker to the frame with brass screws. I tried it with some Herbie's anti vibration material, and to my ears was a big improvement--others may not hear it as much. Cheap tweek and well worth it IMO.
I am also a huge fan of Iso Acoustics products. They offer a return policy and I use them under every piece of equipment. My experience is vibration control will improve to varying degrees, tighter bass, improved imaging, improved clarity and more of a rightness to the sound, meaning it sounds more realistic.
Oh, and a while back there was a listing on Craigslist for some older MIT MH750 speaker cable for $120! I tried them thinking they would not outperform the Morrow cables I had, but to my ears the MIT just sound more natural and realistic, so I sold the Morrows and eventually moved up to the MIT Magnum M1's, so, it may be system synergy, but that's what my ears told me.
I use many other tweeks, but space is limited, enjoy!