Ive actually tried to create the category, but I think I may be doing it in the wrong spot.
As far as the taxonomy goes for audio equipment, I think it would be best to use the following structure to minimize confusion:
...Audio>A/V recievers (a combination of all of the below) EX: onkyo nr905
...Audio>Amplifiers (power amps) EX: Behringer EP-2500
...Audio>Equalizers (parametric equalizers, dynamic equalizers, etc) EX: Behringer DEQ2496 Ultra
...Audio>Pre-amplification (digital to analog converters, etc) EX: Audiosource Pre One/A Stereo Preamp
The idea here being that these products, combined equal an A/V reciever, but should not be classified as such, as they can be mixed and matched as desired. Obviously some of these products are very "specialist", so it would probably be a good idea to avoid pinning them on the main audio page, and reserve the space for more popular/new products.
Update: I managed to create the subcatagories from the audio page.