The rebuttal you link to on xiph.org ignores research that illustrates that humans can in fact perceive frequencies far beyond the classical limit of ~20 kHz. Higher frequencies present essential localization cues. Higher sample rates, like 192 kHz., allow for the reproduction of higher frequencies (assuming playback equipment that can actually reproduce the higher frequencies) leading to recordings which are far more realistic than what is possible with the 44.1 kHz sampling rate.

The difference between 24-bit and 16-bit amplitude resolution is like night and day. As someone that has recorded much contemporary and classical concert music, I can certainly attest to the huge difference between the two bit rates. If you listen to music with a wide dynamic range, then the comparison between the two bit rates is highly noticeable. Quiet sounds can be masked by quantization noise. You want the highest bit rate possible.

Check out The Black Hole in Los Alamos, New Mexico. It's a salvage company with surplus equipment from the Los Alamos National Labs. The place is a huge warehouse packed to the ceiling with old equipment.

You can find lots of scientific equipment, computers, and generally obscure technological devices such as surplus atomic bomb detonating cables for $2.