is there room in the Express for...

hey everyone,  i've read that the only real difference between the pc 
engine and the sgx are two processors for additional speed.  i wonder 
if these (if they were easy to find) could be added to a turbo express, 
LT, or a Duo.  anyone have any ideas out there?  i know there are some 
hardware people here who know or coudl venture a really good guess.