yes, zen is only compatible with bo. you can use the pac, but their quality has gone downhill and i dont trust them anymore. you can try the jl audio if you want. when the sony system first came out, there were no products available so we would high level the front door woofers and tweeter signal directly into a processor such as the mosconi or hertz audison. just needs to be tuned properly. not a lot of shops are expierenced enough to tune, however more and more shops are finally turning towards it. you might be lucky and have a shop near you who knows how to tune properly