A lot of people just call most everything synergy.
I think most of the time (80 - 90% just to throw a guesstimate out) if you know what to look for and can find comprehensive measurements, like Stereophile does, what works together and what doesn't can be explained, but it takes time, lots of research/investigation, and experimentation with different kit/trying things together to get a better understanding.
Say you have x amount of money to spend on an amplifier and you find 2 at your price, a 50 watt amplifier and a 100 watt amplifier. Which one do you buy? The 100 watt one of course because more power is always better. What if the 100 watt amplifier was made for spec games and barely meets its specs on a test bench using 8 ohm resistors and the 50 watt amplifier was built for real world conditions by guys that know speakers aren't just an 8 ohm resistor and it can drive difficult loads without breaking a sweat?