I have 2 X EP-800s in my HT (Audyssey optimized) & 2 X EP-400s in one of my audio only systems (M2s, subs set & tweaked by ear).
I haven't touched any of my sub's volumes since I initially set them up some time ago. Living with subs is not difficult & when properly set up, are most pleasing & enjoyable. My sats & subs audio system outperforms any reasonably priced, mainstream towers that I've auditioned. That's why I chose to go this way.
Just don't overdo the volume & they can blend seamlessly, at least for me in my rooms. Quality subs such as Axiom & other good brands when properly employed will not sound like a passing car playing objectionable noise like Rap.
Each to his own...
TAM
