A quick note about dynamic range, which is what the bit depth affects.
Maximum dynamic range that human hearing can discern: 140dB average
Maximum practical dynamic range of CD: 90dB
Maximum practical dynamic range of 24-bit audio: around 140dB
Dynamic range required for full range live music playback, according to Ampex: 118dB average
Maximum practical dynamic range of high quality studio analog tape: 80dB
Maximum practical dynamic range of studio analog tape in the ’60s: ~70dB
So, if you have a piece of music recorded, mixed, mastered and released in pure 24-bit depth, you *may* hear a difference under ideal conditions (excellent production, good equipment, *quiet* listening room, etc…) Note that there have been double-blind listening tests of SACD, and listeners were unable to hear a difference between the CD version.
All those old Beatles and Rolling Stones albums? Keep the best CD version you have, more bits aren’t going to make a difference.