Hi. If you want to use the Denon as a preamp, you can choose to use the 6000A as a power amp by connecting the Denon's pre-outs to the 6000A's "Power in" inputs, and configuring the Audiolab as a power amp using the front main selector.
You would then only be using the Denon's volume control, and bypassing the 6000A's volume control.
You would then only be using the Denon's volume control, and bypassing the 6000A's volume control.