Location Of Stock Amplifier In Rx350?

[NeoN]

Hi i'm trying to tap into the leads that hook up to the stock amp for my subwoofer and I need to know where the stock amplifier is, anyone have any suggestions? i checked under both front seats and the rears, I didn't see anythng, I checked ontop of the wheel wells and the panneling from the rear seats to the wheel wells, nothing!? could it be in the walls towards the trunk? please help!

ps. I have na RX400h by the way, but i believe both cars are wired the same.