yes it does have multichannel outputs for all speakers , this is what says about the vloume control in the manual.
http://www.oppodigital.com/dv981hd/download/dv981hd_manual.pdf
Volume Control
1. For regular audio volume adjustment, it is recommended that you use the
volume control on your TV or receiver/amplifier.
2. The VOL +/- buttons on the DVD remote control is provided as an
alternative way of controlling the audio volume. It is recommended that
you use this control to make the audio volume from the DVD player the
same as from other sources, such as TV programs or a VCR.
• Press the VOL – button to decrease the volume.
• Press the VOL + button to increase the volume.