How to hook up a subwoofer to a stereo amplifier without a pre-out socket. If you can help with this it would be great. I am hoping to use this using an old Onkyo Integra A9711 amp and 2 x B&W 685 speakers that lack some bass, hence the need for the subwoofer or maybe two? Suggestions on which subs which would be best suited or would complement the setup would be welcome too.