I'm not questioning Cliffy on this, but from my experience (admittedly less geared toward classical music) synthesizers can place a huge demand on a system as well. Some gear just completely punts when it comes to trying to deal with synthesizers. Granted, that's not likely a very big consideration with most audiophiles, but if the artist is using synthesizers and the gear gives up, it's probably giving up with other demands as well.
As an example, Robert Palmer's, "You're in my System" uses a lot of them and if you've heard the song the way I suspect it was meant to sound and then heard it on a system that can't keep up with them then you get an idea of what I'm talking about. It's a tripping song done right or rather bleah when the playback is so-so.
Monty, you are absolutely correct - synths are hard to reproduce well.
There are many recordings of synths going well into the depths with power and richness. A good programmer can put together patches that are exceedingly complex in harmonic texture and motion as well. If you know the recording well one can certainly make a good judgment of the basic ability of a sound reproduction system.
For me the limitation of electronic music however is that there is no real life reference of which the reproduced music is an analog. Electronic instruments sound as they do because of how the sound is amplified once it leaves the outputs of the module. Whether it sounds "good" or "correct" depends on what you like.
However, I know how orchestral instruments sound, both individually and together. I know my own instrument best of course, but I can easily judge a system by how well it reproduces an orchestra.
I have a special love of synthesizers. I first started working with analog Moogs and the ARP 2600 (anyone remember the "Blue Meanie"?) and have continued playing with the various forms of digital synthesis and samplers. They now are just fun for me - but they are still great to power up and play. By the way, R2D2 of Star Wars is voiced by an ARP 2600.
Amusingly, I have never heard anyone talk of how different patch cords changed the sound of their analog synth.