I just purchased a new AVR300. It sounds absolutely great with my old Quad ESL57 speakers in stereo mode (I do not yet have my surround speakers). On the ohter hand, my old Velodyne F1500B subwoofer sounds terrible - soft and inarticulate. Before using the AVR300, I had an old Lux integrated amplifier. I had the the Quads and subwoofer wired serially, through the speaker terminals. The sound was was tight and deep. With the AVR300, I have the subwoofer hooked up through a line cable running from the sub output from the preamp section of the AVR300 to the line input connector on the subwoofer. Does anyone have any idea why it sounds so poor and what I can do to improve the sound?