It's true, you can't. The iPod won't play anything over 16/44.1. iTunes, on the other hand, will play anything up to 24/192 IME, as long as you have an external DAC that can also go up that high.
That said, I have not tried loading a hi-res file onto an iPod, then connecting the iPod to a dock like the PURE i-20 and the dock's device to a 24/192 DAC. Maybe someone else here has tried that.
That said, I have not tried loading a hi-res file onto an iPod, then connecting the iPod to a dock like the PURE i-20 and the dock's device to a 24/192 DAC. Maybe someone else here has tried that.