Yesterday I was reading NwAvGuy's update on his ODAC design and he asserted that 192kHz is a very glitchy sampling rate, and that more often than not 192kHz tests and sounds audibly worse than 96kHz in real-world use.
He also pointed out that 24-bit performance is a bit of a pipe dream, and that the *effective* (real-world) bits of many less-expensive 24-bit devices is around 16. He tested the Benchmark DAC-1 at 19.3 effective bits, which is apparently about as good as you're going to get at any price.
