Many times, measurements in isolation, in the laboratory, miss the multitude of variables at play in the real world.
For example, measuring a speaker in an anechoic chamber is far from real-world. People do not actually use speakers in an anechoic chamber. Speakers interact with the rest of the world, including the quirks of the electronics driving them, the room, and especially the listeners' ears. Thus, "cabinet resonance" in the real world is not necessarily a bad thing if it interacts well with the total surrounding environment, just like cabinet resonance in an electric guitar is not necessarily a bad thing... Speakers, particularly, are the chief resonators combined with room and individual ear resonances. To write off a speaker because it "resonates" is overlooking the fact that the universe resonates; it's the overall interaction that matters, the environment matters. Stereos do not exist in abstract space; in use, they interact with the real world.
Likewise, amplifiers have their quirks, their individuality... and there's laboratory, and there's real-world. But even in lab, there will be measurable differences, but which measurements translate and how they translate to my ears or yours is an entirely other question. Plus, we all have subjective preferences as to sound ... ears and minds differ.
Bringing me to my last point: some have said "your room is the most important component"... but I disagree. Your EARS combined with your mind and personality is the most important component-team. Ears matter; case in point, high frequency loss due to simple aging, loud noises, etc. etc. but even without "loss" we all have different hearing profiles from the get-go, so a "perfectly measured" amplifier for example may sound worse than a "treble skewed" amplifier to my imperfect ears. Likewise, to my ears, room, speakers, habits, purposes, and preferences, I may prefer a lusher sound profile rather than a "laboratory clinically perfectly neutral" profile. Then, toss in the fact that mind and personality can be educated, and preferences can change, and purposes can change, and ears can change... laboratory measurements really cannot reflect all these real-world considerations.
It seems to me that (other than ears...) speakers are the most personal no matter how they measure, although measurements may help explain WHY I like one speaker over another - ah, the treble measures bright, nice! helps compensate for my ear's dip in sensitivity up there - then amps, and very lastly cables.
Measurements are a start, though, for sure. But all those electronics still have to interact with your quirky room, and your own ears and mind are the ultimate endpoints.
Finally, there's this: folks: get your ears checked -- some of the most amazing pieces of audio equipment are the very recent, like in the last two years, excellent customizable hearing aids; yep, that's right! Phonak Audeo Paradise and Widex Moment come to mind; micro-technology at its finest. Short of laser eye surgery for the ears, they may be the most significant piece of tech you can add to the chain.
