A:Answer The subwoofer output is a PASSIVE output, meaning only the signal is provided; this type of A/V receivers rarely ever provide an amplified/powered subwoofer output.
It seems you already have an awesome Subwoofer model from Def Tech, --which is SELF-POWERED already, it has a very powerful built-in amplifier, so all you need is to feed it the RCA-type signal cable coming from the subwoofer/LFE output of the Denon receiver, plug the power cord... and secure all object on your walls, because that little sucker is going to shake your foundations... have fun!