I agree and disagree.
I can tell the difference in inter-connectors and cables but to a degree. You do need a "decent" set of separates and speakers and more to the point, a decent well tuned set of ears.
Mains cables is just a hoaxs I say. The only time a mains cable could make a difference is if that mains cable was shielded and your laying the mains cable close and in parallel with interconnects and speaker cables. Ill admit I know little about building amps but what I know about electronics is that once a transformer has stepped down the voltage a voltage regulator is used. So whether the transformer gives 20, 24 or 28v it will always supply the circuit with the voltage the VR is rated for.
Now back to the ears thing. You take your average person and they can't tell the difference between cheap and expensive cables but if knowing what each cable costs they would have you believe the more expensive ones sounded better (I call this the Festool effect). In many cases there brains will tell them the more expensive onces sound better because they expect them to. Now for someone with a tuned set of lugs, they generally can and the proof is when they can say that the more expensive cable isn't matched to the system and gives a poorer sound. One expensive cable can sound brill on one set up but pants on the next, as you say, impedance matching and resistance in the cables.
On my setup I use a mix of cheap, budget and expensive leads. It depends on which speaker and which device.
Like all things having the best is always nice but not needed. Having £1000 leads might make a difference to the sound but does it really add that much to the music from say a correctly set up system would give you. Does not having the best or even a perfect setup detract from the sound?
Me I think not. Its all margins, every little it in. I haven't bothered upgrading to BluRay, DVD looks like real life, its a good clean picture even on my 83" screen. I don't see that I need more resolution for movie watching, I don't see that I need more vibrant colours (but does it? Ill get around to this) and I don't see that a cleaner picture when watching real film (ie not cartoons and animation/cgi) is really that much cleaner.
Ask yourself, why make adverts containing stunning colours and effects that wow you to advertise HD when they are assuming your on a non HD TV? Surely you wouldn't see the stunning colours and effects to HD standard. All but you do, a well toned TV will display colours at the same vibrance (within its range) as an HD TV. Its back to what has already been said, cleaver advertising and the human need for better. HD is really just a better pixel count per inch.
When watching cartoons, films filmed in cgi or animation on Sky HD or playing xBox I can clearly see the difference between HD and non HD, but watching real life films the difference is marginal. My point in the HD is with the average music listener, its them in the know that can tell. To further explain my point, when me and the other half go into the cinema, I will say (if I hear so) that there is something wrong with the sound, she will say it sounds no different to how it normally does, then get annoyed as ill start playing with the settings.
