Try using https://pqrs.org/macosx/keyremap4macbook/ to remap the 3 media keys to F7 F8 and F9. Then use the F-keys as the triggers in Alfred. If you want to keep the ability to control iTunes using those keys you can map fn+mediaKey back to the its original function.
So if you press next keyRemap4macbook changes your press to F9 and triggers alfred.
If you press fn+next keyRemap4macbook changes your press to next which triggers iTunes.