Use the visible in render option to make the part invisible until what ever frame and to make them grow. you can key frame the size using the scale tool. If you want different parts to com in at different times seperate them into groups of objects rather then just one.
With simple speaker box and stuff PLA (point level animation) can be used really easy for that.
As for speakers you need to build them with several pieces and animate them in at different times most likely using the scale tool.
I would suggest placing your geometry in a Null before scaling anything so you can always revert back easly.
/randy