ok ill try to explain its kinda hard to someone who doesnt really know but here it goes.
all amps runn power at differnt ohm levels
most digital 1 channel amps put out there maximum power at 1 ohm or 2 ohms so in order to get that you have to hook up subs in the right configuration to get 1 or 2 ohms jl audio sells subs in dual 4 and dual 6 and i think maybe even dual 2 possibly, figure if you get 3 dual 6 ohm subs and a jl 1000.1 you want to hook it up to one ohm so you can run the full 1000rms right??? well thats why youd get 3 dual 6s or two dual 4s, 3 dual sixes in a parrallel/parrallel config would give u the one or 2 dual 4s in a parrallel parrallel would give you one ohm, it just matters on what your amp runs the power u need at what ohm to decide on what sub config u want, most 2 channels are only 2 ohm stable so you want to get 2 dual 4 ohm subs so you can run each channel at 2ohms (each sub hooked up in parrallel)
do you understand at all? or did i just confuze you more?