Remove the cluster, remove the speaker from the circuit board, attach 3' long wire leads to the speaker contacts on the board, run those wires to a small 10-20watt mono amplifier (eBay, $10 or so), attach a small 3" speaker to the amp, run power to the amp from the headlight low beam circuit so it's only on when the headlights are on, adjust volume to your preference and hide the amp and speaker behind the dash or lower center stack.
Easy
