A more correct statement by the salesman would have been: "a really high end system can make most mediocre recordings more enjoyable to listen to."
While we can't expect a great system to file down all the "warts" in a bad recording, we can expect that if there are latent redeeming qualities in those recordings a better system will extract them and toss them out in the listening room for all to hear. (Yes, room acoustics matter, too).
We are involved in performance modifications, and always perform before/after listening tests with our customers. We put together a reference CD that includes well recorded music -- AND, intentionally, a sampling of poor recordings. Improvements in sound quality produce a more organic, fluid sound with more authority, and less harshness, strain, and edginess. All these improvements are "friendly" to a bad recording, not acting as microscope revealing every flaw, in my opinion, provided there IS something more to the recording that we're not hearing on a lesser system. In our experience, the bad recordings sound much more musical, and less repellent after our performance upgrades.
Another overlooked element is the physical media itself. My experience with the Audio Desk CD cutter along with Ultrabit treatments has been eye, and ear, opening. I understand the term "analog-sounding" is overused, but results on my favorite recordings were astounding. On the subject of bad recordings, my wife ordered a compilation on CD that was downright unlistenable (to me). I thought I'd have nothing to lose by trying the "full CD treatment" on one of the discs. Much to my surprise, the CD had greatly reduced, harshness, improved dynamic range, and more balance. I can actually sit in the room with her and listen to them now. Without prompt from me, she mentioned that the CDs sound much better than before.
