I've done this and more
I was downloading MP3's since napster first came out, before it was popular, when 128kbit/s was the best quality you could hope for, I knew it wasn't up to snuff, but for "free" it was good enough.
Fast forward somewhat and the pirates obviously decided broadband was pervasive enough to bump up bitrates to 192kbit/s, which was a clearly audible difference; fast forward again to today, and we have 320kbit/s being standard, a night and day difference from those early 128kbit/s files.
Since I have listened to countless MP3 files throughout the years, often "upgrading" my old copies with new ones, and following the progression of encoders such as fraunhoffer's, as well as encode engines like lame, I realized early on, the encoder makes the biggest difference.
The rise of the format spurred a lot of developers to write cd-ripping software, while others wrote mass WAV->MP3 encoders to fulfill the needs of users, obviously these time saving efforts didn't focus on quality, nor did the subsequent wave of combined ripper+encoder software.
I had tested 4 major encoders back-to-back at various points in time, the fraunhoffer being the defacto quality standard (hey, they had a whole institute behind them right?), and I can unequivocally say, most encoders sucked balls. Even at higher sampling or bitrates, many encoders either chopped off too many frequencies in their quest to shrink files, or used simplistic
hacks to excite the music to hide the flaws. I found the state of things to be quite terrible.
Then we also had the player wars, Sonique and Winamp being the popular ones with the kids, each played sound just a little differently. If you search the internet archives, you'll see countless press releases of improved sound rendering in the engines, each company extolling how awesome their next one will be. I theorize that in the early days, it was all about artificially re-inflating the deflated MP3 audio to sound like it wasn't butchered, and then as MP3 quality improved, the engines slowly removed most of these "enhancements" to be "more realistic".
Why was I able to hear the difference? Well, having worked very hard at creating my ideal speaker setup, it exposed all the flaws, imbalanced resonance, those cymbal artefacts you mentioned and more. You assert there's no standard for speakers, but there is, indirectly, they are called "reference" speakers. A quality german or japanese 3-way "reference" speaker like the ones I had are going to be big, and it may seem ridiculous paired with an underpowered computer at the time, but sound was important to me. They turned my computing experience, into a faux studio experience.
I should mention that I worked in the P.A system, and overhead paging field as both installer, and as a sound theory specialist. Many of my jobs revolved around taking a noisy building, like a pumping station for the city, or giant packaging facility, and fixing the mess some inept previous installer made. The typical problems were mismatched audio loudness, general direction and sound reflections, which all lead to one thing, blurbling... ie. you hear it, but it makes no sense, and for that they failed their safety inspections. This often meant I spent weeks optimizing for clarity and volume, followed by a new inspection (they all passed).
Much later, I also discovered a dirty trick: some CDs are produced with low quality sources, the compilations people buy are very often inferior to the original source CD. The only reason for this that I could see is that the author/compiler takes the music form whatever sources they can find, does some basic mixing (or worst case run them through an autotune/normalize function ugh), applies for the relevant publishing licenses, and then prints the disc... I have ripped and overlaid the tracks of identical songs in sound editors to find deviation, it was huuuuuuuge.
My advice, get the original CDs or as close to untarnished/remastered source (or lossless file), and make your own mixes if you still want to listen to them on CD, such as in a car. I don't trust any of the MP3 playing headunits to reproduce the sound that well, they still bias/enhance the audio unnaturally.