There's normally option settings for Auro (Strength and size or whatever it's called). The strength setting greatly affects Auro's bass output. I really think they missed something in the decoder there as it shouldn't affect bass like that (I've got a REW plot showing the effects on bass as it's turned up. It really gets crazy). But a setting of around 6 for strength is within a dB or so of flat. I just leave it there for that reason. Otherwise, I'm having to fiddle with the sub level, which is annoying.
Yes, it is annoying having to mess with the controls all the time. I'm glad you noted the issues with the Auro strength. I do find that the default Auro strength setting of 10 is often too high, but sometimes 6 is too low. Plus the region of mid bass that it mostly affects can make a system sound like a stereo-in-a-box from KMart.
I would be curious to hear your observations about Logic 7 and how you'd describe what it did different by comparison. I always wanted to try it out, but Lexicon was out of my price range back then and HK lacked adjustability. I'd also be curious to hear how its effect differed from the Surround Master as I've been thinking of getting one when V3 comes out.
Lexicon Logic7 (L7) was an interesting beast. In a 7.1 system with rear surround speakers placed towards the ceiling, it had an ability to imply height to a presentation. The adjustable L7 was truly prodigious. Adjustments included: Vocal Enhance; Surround Rolloff (567 Hz to "Off"); Rear Delay (ms); Film, Music or Music Surround modes; Bass Enhance; Sound Stage (front, neutral, rear); Tilt Equalization. It could also upmix from 5.1 to 7.1. The 5.1 to 7.1 upmix algorithms were different than those used in the stereo to 7.1 modes.
What came out of it could be anything from spectacular to horrid. One of the problems with L7 is that it spread bass frequencies to all speakers such that material with strong bass would sound way too strong. The Bass Enhance function mitigated some of the problem, but I found that it introduced phase issues, at least on my setup. The excessive bass still sounded better than that produced by Auro 3D, but there was no way to mitigate it except by switching to another codec such as PLIIx. On the other hand, content with normal to low bass content sounded magnificent.
As with Auro 3D, L7 could take a recording with a lot of embedded ambience and transform it into an ambient mess. PLIIx also did that. Dolby Surround is even worse. For these recordings, I find that the Surround Master works best.
The logic circuits in L7 were "intense" and produced a lot of front to back separation. When upmixing certain stereo material, i.e. 60s pop, it would often produce pumping artifacts. I have not heard these artifacts from PLIIx, Neo 6, Auro 3D or Surround Master.
The things I miss most about L7 are the Surround Rolloff and Tilt Equalization. The Surround Rolloff was exceptional for processing some gnarly recordings...I could keep decreasing the surround rolloff frequency to minimize the crap extracted from these recordings and routed to the surround and rear speakers. The only way to approximate this feature with Auro 3D in my Marantz is to use the graphic equalizer, which I find inconvenient.
Tilt Equalization in the Lexicon processors was the most effective tone control I have ever used.
Whenever the Surround Master sounded anemic, I found that L7 (and now Auro 3D) sounded better...although the workaround with the Surround Master is to crank up the rears substantially.