an option for you would be to see if you could trade out your seat backs (that would contain the armrest/cupholder) with someone who has taken theirs out for a sub box. see forum link below.
http://www.cruzetalk.com/forum/36-electronics/3283-my-audio-build.html
not me.
http://www.cruzetalk.com/forum/36-electronics/3283-my-audio-build.html
not me.