Relationship between sampling rate and number of levels/bits in PCM
The solid lines in the graph follow the squares (i.e. have low resolution, for instance 8-bit), while the dashed lines have about 3 bits higher resolution, giving 8 levels per square. We see that the dashed line follows the curve closer than the solid line, even when the sampling rate doesn't change; we have 1 sample per 2 squares for both curves.  

The sample rate is dictated by the Nyquist/Shannon sampling theorem, which says that you have to sample at least at twice the highest frequency in your signal. For audio we usually assume 20kHz as the higher limit, and so the CD's 44.1ksps (k samples per second) is sufficient to reproduce the audio signal. How accurate depends on the number of bits. The 11-bit sampled signal will follow the 8-bit signal more closely, and a 16-bit signal will do even better. Even at the same 44.1ksps a 64-bit resolution will still do better (even if in practice this is impossible to achieve).
So it all depends on what level of accuracy you expect. An 8-bit signal will not be acceptable for HiFi, but higher than 16-bit does not give an audible improvement.