Your computer will be fine for this task. 4GB memory is enough if you are dedicating this computer to just playing the music and doing sound processing for the radio station and not running anything else on it. The processor is more than adequate, you will be able to run the declipper to ensure high quality input audio as well as all FM processing you wish.
You may want to upgrade to 8GB and change your Windows to 64-bit, but it will work in this configuration as well.
Friend, I will use the computer with an audio input card and the same plate put the MPX output.
How serious the minimum configuration to run the tool with the best stereo preset FM, a complete preset.
What do you indicate as smaller computer, to have a satisfactory performance.
After all, with the crisis, we need to save!