There's a reason that most SQ decoders are poorly regarded: they barely work at all. As I said earlier, a full-logic SQ decoder such as Sony SQD-2020 or a Tate will sound amazing. Other than a built-in Full Logic on a Lafayette receiver, or a Marantz SQA-2 plug in module, which only fits Marantz receivers, all built-in SQ decoders I've heard are poor. With a non-logic decoder, as in QX-4000, SQ stands for "sorta-Quadraphonic."