What kinda numbers we talking? Like .7? or somethin real weird and low like .35?04 model, and wring a d2 and d4 together will just give you odd number ohms, but there are amps that can run them
but you would have to realize that the subs would be getting DIFFERENT power...i believe you can get 12, 3, 2.67, and .67 ohms. thats all the common combinations