I finally put my finger on why my Arc/Sub combo sounds worse than it should, and now I've found multiple posts mentioning how pairing a sub with an arc neuters the sound. I completely agree. The crossover point is set too high and too steep. Once paired, the arc sounds like it has no low end at all and the sub is distracting because it is handling too much. Not all rooms are the same, I'm not moving the sub, arc's are used for music not just tv/movies, we don't all have iphones, and I doubt trueplay would do better than my own ear. We need more tunable crossover settings, including disable.

I figured that out when I set up an Amp today and was dismayed to discover that using the sub out connection forces a (albiet somewhat adjustable) crossover on the main outputs. Disabling the Amp crossover should also be an option. Fortunately my sub has speaker level inputs so I don't have to use the sub out connection, otherwise I wouldn't be using the Amp now. Once I realized the Amp forces a crossover when sub out is used, I realized the same thing had to be going on with the arc...I unpaired the sub, and the arc sounded better without it. 

The arc plus sub sound profile reminds me far, far too much of old Bose cube systems. Please don't continue down the path of small speakers and subs with forced eq settings that don't help enough but fool people who don't know any better...I want to like Sonos.