Actually, Foobar2000 does an excellent job at playing back the VGM files and outputting the WAV file. I suggest that you ditch AO for it since the former is a very outdated program from 2007 that's no longer being supported.
You can start by downloading the latest version of foo_input_vgm from
here. There should be a lone white button beneath all the text. Wait until it downloads and install it. Also, make sure to disable (untick) GEP's VGM playback beforehand, as its core is older and it'd cause conflicts between the two plugins.

Now, to disable individual channels in foo_input_vgm, navigate to "VGM input" in your plugin library, then go to "Chips Options" and in the first drop-down menu select "GB DMG", the Gameboy's sound chip. Here you can enable and disable individual channels by (un)ticking them. I believe it should affect the VGM immediately, but if it doesn't, try stopping the song and playing it from the beginning.
I think you already know how to output a WAV file in Foobar, but in case you don't, right click on the song -> Convert -> Quick Convert -> WAV.
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Not a regular ripper anymore, sorry.
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