A very popular communications forum had a great article on optimizing the audio settings for your Astro25 radios. That forum is no longer running, so I thought I would take the opportunity to document the settings here.
All AGC is enabled. AGC Output is -3, total is 12. Noise suppression enabled. Attenuation level: Advanced.
Of course, your mileage may vary, so feel free to try and find the settings that work for you.