i would avoid magnets.
if it needs to be easily removable, it really depends on the design of the cabinet, but if there is wood at the back by the monitor then i would carve a slot in the wood to put the back portion of the control panel into then use the magnets in the front area to hold it down.
inserting the panel would be something like:
hold the panel at a 45 degree angle and insert the top portion into the slot
rotate the panel down until the magnets catch to hold into place.
but it really depends on the cabs original design.