Lexus is220 - tinkering and help!

[JC12]

Hello!

I picked up my is220d SE-i today and super happy to be back in a Lexus (its my 3rd) even if it is a cheap but value for money car! 

Ive got some plans for it but mainly just upgrading things, Im not really into modding however I like to get my cars to as good of a standard as they can be while keeping as stock as possible. At least from a visual perspective. Im looking forward to tinkering with this one. 

My first Question:

Id like to upgrade the rear speakers, as far as I can tell, they are useless or past their sell by. My previous lex as the ML sound system but as far as I can see this is pretty basic. 

How easy is it to fit a "OEM" sub in the parcel shelf behind the rear seats? I dont have the Nav system and the oem stereo unit doesn't give me the "sub" volume option so I can imagine it will run off the "bass". 

Or, would you say it is easier to install and active underseat sub for a bit of extra punch, which I dont really want to do , id like to keep it as in keeping with the car as possible. 

 

Thank you!