[Where Can I Fit More? What Can I Fit?]

pic of doors front and rear doors might help

heres different pictures i got of google cuz i dont have pics from the interior of my car but it looks just like this...

[Where Can I Fit More? What Can I Fit?]

I just started to buy some components for my mercedes 300e but u can only put 8 speakers in total 2 in dash 2 in rear, i was thinking about putting in at least 4 more speakers but i dont know where... maybe u guys can help me out, i want something that would look clean cuz i want the car to look stock but have a good system where can i put these extra speakers?

Oh and I'm barely looking into buying rims for my car since a while back i bought these rims of my uncle and they look pretty sick but i wanna upgrade now... do u guys now if i can put some 18's on the mercedes? 18x8.5 front 18x10 rear? im new to this so yeah please help

thanks