subwoofer to digital music and movies


I am a bit confused on how to best play music and watch movies with my new subwoofer. My recent purchase was an Earthquake Supernova MIV 15 inch sub. My 2 channel music listening is all digital via Benchmark DAC1 used as a preamp and for home theater using my Marantz AV7005 preamp. Question is: how do I best connect the subwoofer such that it is part of the 2 channel listening experience (Benchmark) and playing movies using my Marantz preamp? 

Simaudio w5 (2 channel amp)
Earthquake Cinova Grande (5 channel amp)
Von Schweikerts VR4 + center + surrounds 
Benchmark DAC1 
Earthquake Supernova MIV 15
Marantz AV7005
OPPO 105
128x128ghulamr
Thanks for the reply and it makes sense. The sub I have does not have the DSP and is one level lower supernova MKIV - which happens to have the high level input along with the LFE and hence my question on using both. 
Earthquake is great. The form factor is big and not pleasing to the eyes in the Family TV room. What I’ve heard of the REL’s is that they are for both music and HT and can be connected to both at the same time. Not sure if Earthquake can. 
REL is garbage for home theater and any music with real deep bass. Only good >35Hz.

Rythmik, HSU, JTR, PowerSoundAudio, and SVS. These are the only major brands selling >$500 subs that have a good bang for buck.