Paul,
Keep in mind that the EP 500's power amp output is related to the pre-amp's input voltage signal...can't really compare HT sub settings as different pre (receivers\stand alones) linearities will be different!
My EP500 volume setting changed from 7 o'clock (Sony Receiver) to 8 o'clock (Emotiva pre\pro) to maintain flat output in my surround system. At the 10:30 o'clock position, your receiver's LFE pre signal probably is somewhat less than most, but you should still be driving the 500 power amp the same with plenty of dynamic headroom!!!
Don't fret, the Axiom DSP in the amp's signal path should provide you with bullet proof performance...Enjoy!
