Using MCU to supply SPI signals to amplifier chip
I would say that you want to look for the smallest uC possible that can run at the desired frequency. Since you are only going to use it to transfer the data using SPI protocol, it does not matter if it is an 8, 16 or 32 bit uC - you will be transferring bit by bit anyway. The other question is how you are going to generate the commands for transfer. Or they will be simply stored and read from memory? 

And keep in mind that your maximum clock frequency can be 24MHz, and since you are new to electronics, you will be better off starting with a microcontroller, as opposed to an FPGA.

You did not mention anything about wireless communication, what is going to send information and what is going to receive the information, so my answer assumes that you want to substitute the FPGA with something simpler.