Would adding another sub to my system help give me more b?

i have 2 sony xplod 12 in 380w rms subs in a slotted box powered by a 1200w max sony xplod 2 channel amp. would i gain anything from adding a 10 in jl audio w1 300w rms sub in a separate box to my system? i have power wire that would supply enough for another amp. i can get the sub for about $50 with box but is it worth it?