hi guys,just got my first taste of a sub sort off! only from my 1 pair of b&ws 686s which i will move to the back when money allows but would a sub be the next thing to spent my money on or a centre im thinking 1 of these ASW608 but would it fit in now with 686s at the front then also when they move to the back and 685s are at front? amp is a denon 1909 any help welcome cheers ps if thats what 686s can do im not looking to go ott! well not untill i get a house with its own grounds