Hello Gazza...
Please add a category for guitar amplifiers. I note that 'Musical Instruments/Prof. Audio & Equipment: Amplifiers' is not a good choice for guitar amplifiers (or bass guitar amplifiers for that matter).
I think it would be best located like this:
Musical Instruments/Guitars:Electric:Amplifers
And:
Musical Instruments/Basses:Electric:Amplifers
Thank you very much...
Bill
M.E.S. Music Equipment Sales Ltd.