2^24 = 16,777,216 Microvolts, I used to work on receivers with .1 - .15 uV/12db Sinad and those voltages are 10X 1 bit in 2^24 bits/1V (impedances adjusted) Lower and If I factor in a 6 db drop due to power/voltage relationships that's still close to the noise figure of most fair to good A/D's.
Preamps, SURE if for only improving the signal to noise ratio.
Bob