Hi,
you have a problem, but not with the cpu speed, the problem is dinamic range, several years agoo i start project with one university, then we can contract the price, but i start the research, different specialist have a different point of view about the dinamic range. But the final requariments was be for a 24 chanel 24bits resolution. The frecuency is not very High, 1000 is more that enought, the real input frequency is not highest that 20 Hz. But ADC with true 24 bits resolution is a very difficult to find. ........my plane take off .. i will write leter.