I would seriously consider using a telecom ring, instead of a box.

Are those the orange things in the electrical aisle at HD? G

I have just plain speaker wire off a spool ran through the stud/ceiling
cavities to the far corners of the room, terminated in single gang
boxes with two-port levitron wall plates (red & black screw down
connectors).

I have CAT5 wire and some RG whatever I had lying around from the cable
company kit sent with the high-speed internet service, using hex-crimp
connectors. Just basic stuff is all I need.

Thanks!