plants can live in there .

u said u will use 2 60w cfl . how much lumen have they ?

smart thing to do => on the top of speaker box goes cfl's . under them put glass in square format 2 feet x 12 inches so u will get more vertical space because u will eliminate heat produced by cfl-s.
on side of box where are cfl put one 120 mm pc vent to blow heat out .
On each side of box where are plants put 80 mm pc vent to blow fresh air in .
With glass under cfl-s witch is stopping heat , u can install more
lights .
Watch out on light leaks .
U will probably need to start flowering a little earlier then others .