I am looking to increase the mid bass in my 2018 Ram 1500. I have run out of stock locations but I was thinking I could add some smaller speaker in an amp rack I a building behind the back seat. I have about 5 to 6 inches of clearnce for these speakers. So my question is would it be better to go with two eights or four 6.5's?. I am looking to cover about 80 to 400 hz. My main concern with the smaller speakers and higher frequencies is that they will be deadened by the fabric behind the seat. Any thoughts?