Well I `am using the 4 Subs KW-120 stacked behind the 120 perforated screen and on top of the stack I put the KL- 650`s , the Center is also at the same height . They are in ear height when sitting just like the 650 backs and the KS- 525.
Going from 2 Subs to 4 subs makes a big difference on impact you don`t need a back massage after listening at high levels, it is great