First off, you mentioned Transparent Cables making some claim about resonance frequencies. I've looked at their web site and I didn't see ANYWHERE, where they mention this.
Now, when you have a big home stereo and you crank it up at reasonable levels, things in the room will vibrate because of certain bass frequencies, right? Maybe that's what they are talking about. Now, is that going to affect the sound system? Heck, I don't know if that's audible enough, but all they want to do is control the amount a cable is going to vibrate when you turn the system up, then that's what they are doing. I know that high current power cables have eddy current going through it and it might leak into another cable that's susceptible to noise. That's one issue these guys might want to deal with. I think those cable blocks they use are more for cable management to make sure cables are separated from other cables, and maybe to keep them isolated from the floor. Cable blocks or whatever you call them is fairly inexpensive compared to the price tag of these systems, and I wouldn't get all weird about it either way. If that's what some feel comfortable doing, then that's their thing.
Now, when it comes to different cables sounding different, I suggest you go to MIT Cables' website and READ and get to a point where you can comprehend EVERY SINGLE Technical Whitepapers, etc. They actually use some of the most precise test measurement equipment used in the audio equipment design/test industry and they are performing tests MOST people, EE's or otherwise, don't know much about. What I'm referring to are Articulation Measurements. They run a test to get a "response curve" of an analog cable. This PROVES that cables inherently act like a filter, which is what cables do to an audio signal, they filter the audio frequencies which in turn affects the sound, for the better or worse. Some can hear those subtle differences, some can't, and it's dependent on a LOT of factors. It takes time to evaluate what is going on since some cables make only make an improvement over and other cable with certain frequency ranges on certain equipment. Cables also have different impedance as does pre amps, power amps, speakers, so some cables are just better suited for certain equipment, which is another reason why some cables might work better or worse, and then there is the subjectivity, which is the listener decides what they like and don't like, that's all personal taste, just as some people like Panel speakers, others like traditional drivers, some prefer folded cabinets, some prefer compression horns, some prefer dome tweeters, etc. etc. etc.
But as far as resonances are concerned, I think they might be talking about when you turn up your system that cables physically resonate to certain frequencies (bass frequencies is my guess), just like things in your room might vibrate, like windows, tables, etc. etc. So maybe that's why they get those blocks to hold a cable in place.
