Sorry, but you are wrong!
DI boxes take an instrument level signal and turn it into a mic level signal. They do not amplify a signal to line level (usually, some newer DIs do have a line level output as well)
They were originally designed to send instrument level signals from stage, through the multicore, and into the mic channels of the mixing desk, so that the instrument level signal appears at the input of the mixer as if it was a mic input.
They do not amplify the signal.
It is usual for the XLR out of a DI to be mic level, and if not then it is usually has a second output marked as line level.
Simon
Canberra
AUSTRALIA