naw i'd stick to passive intakes. wasn't the inside of that cabinet white? if it was, you're probably not getting much more reflective-ness (is that a word?) with that blanket.
mylar - 95% reflective
flat white paint - ~90% reflective
aluminum foil - ~50% relective

i don't know if i'd keep that in there. maybe just get some flat white spray paint (assuming the white in there is glossy white) and get mom and dad involved with a little painting day.