04 140bhp Vvt Radio/stereo Question, Expert Help Requested!

[marvo]

Hi folks

I have been trawling the various forums regarding the issue of upgrading my Celica 140bhp VVT 04 reg stereo system.

At the moment I am confused as to whether I will need fillers, what types of head units are best for decent sound, whether or not there is a separate amplifier somewhere on the car and if so how to use/bypass/find it. There seems to be a plethora of answers to choose from!!

My questions are these.., is there a definitive guide on Celica sound system upgrades? Does a circuit/wiring diagram exist?

Are the Speakers easy to replace or is it a nightmare?!!

It currently has the Toyota 58806 CD unit fitted, poor quality sound and no mp3 or SD functionality.

Any help would be appreciated and if I do actually end up replacing the system I'll do a step-by-step tutorial with pics and/or video for the next person to ask the question!! I'm also asking this question on other sites in the hope the best one will give me the answers I seek!!

thank you all in advance,

Phil.