Hi Mate, I recently had a go about replacing my Toyota Avalon Stereo with another Toyota stereo, and it wasn't fun, as the wires that connects from the stereo don't connect to the speaker, they connect to an amp, the location of the amp is the painful part, it is hiden behind the driver airbag, you would need to access it from under the passenger footwell. (I have a Mark II VXI, which has the Six Stacker unit ,4 speakers and 2 twiters). To be honnest, I couldn't reach it, as I saw that there were alot of devices in there (e.g. Cruise Control unit), however, if you take the facia stereo out, you can spot it (hiding in the far left, behind the airbag activation mechanism). BTW, I didn't change the stereo, I just fixed my old stereo, so I wouldn't have to deal with the amp. I am sorry I can't be any further help, and good luck with this.