2 - Effects of Cable, Loudspeaker and amplifier interactions, an engineering paper from 1991.
http://www.apiguide.net/04actu/04mus...teractions.pdf
Twelve cables are tested from Levinson to Kimber and including car jump leads and lamp cable, from $2 to $419 per metre. The results are based on the theory that loudspeaker cable should transmit all frequencies, unscathed to any speaker from any amplifier and loss is due to resistance. There is an assumption that letting through more frequencies with less distortion will sound better. But that seems reasonable to me.
The best performance was with multi core cables.
The car jump leads did not do well and cable intended for digital transmission did! The most expensive cable does not get a mention in the conclusions, but the cheapest is praised for its performance and
Kimber does well. Sadly there is not a definitive list of the cost of the cables and their performance, so it is not clear as to whether cost equals performance, but the
suggestion is that construction equals performance.
3 - Do all amplifiers sound the same? Original Stereo Review blind test.
(The original Bruce Coppola link is broken, this link is the best descriptive of the test with soem of the original images, I can find)
http://www.hometheaterfocus.com/receivers/amplifier-sound-quality.aspx
A number of amplifiers across various price points and types are tested. The listeners are self declared believers and sceptics as to whether audiophile claims are true or not.
There were 13 sessions with different numbers of listeners each time. The difference between sceptic and believer performance was small, with 2 sceptics getting the highest correct score and 1 believer getting the lowest. The overall average was 50.5% getting it right, so that is the same as you would expect from a random guess result.
The cheapest Pioneer amp was perfectly capable of outperforming the more expensive amps and it was ‘striking similar to the Levinson‘.
As an extra to this and for an explanation of how amps can all sound the same, here is a Wikipedia entry on Bob Carver and his blind test amp challenges
http://en.wikipedia.org/wiki/Bob_Carver#Amplifier_modeling