You use a system that has at best 12 bit resolution (amplifiers, speakers) to decide if 16 bit sounds better than 24 bit. Great.
What was THD+N of the chain? Speakers have at best 0.1%. That's -60dB. That's less than 11 bit resolution.
In my experience there are some marginal/poor sources (I own them), less dynamic and bandwidth than CD theoretical limits:
Pink Floyd, Dark Side of the Moon SACD
Steely Dan, Gaucho, SACD
Alan Parsons, I, Robot DVD-A
Another issue: Did you ever try to use a true multibit DAC when you play PCM? With headphones?