Guys, sorry for the delays. I'm working on finishing a PhD, so time has been limited.
I have done a number of comparisons, taken notes, and will post more detailed impressions when I can. For now, a summary. Keep in mind, your ears are different than mine, and so is your room and how you place your speakers.... so your results might be entirely different.
*** It's also important to note that much of the movie/TV show demo'ing was with Audyssey Dynamic Volume engaged (yes, run different times for different speaker setups) in evening or midnight mode. I live in a connected townhome, and when watching/listening at night, which is when I've had time to do most of the movie/TV demos, I can't get around turning Audyssey Dynamic Volume on (and it's how I generally use the speakers for movies, so important to test them that way anyway). From my experience, Dynamic Volume can do some unpleasant things that make deep voices sound a little boomy. So bear this in mind when I make comments about these speakers with dialogue. Still, the general trend remains - if the speaker was a little too full in the bass to begin with, Dynamic Volume just makes it worse. For all A/B music comparisons, I had Audyssey entirely turned OFF.
HTD Level Two - The light cherry Towers (well one of them) were the nicest looking speakers of the bunch, and cabinets seems the most solid. Problem was, the pair was very mismatched, both in color and grain, so there were going back regardless. Luckily, they were also my least favorite sounding speaker overall. They had the best bass extension and punch (quality was pretty good too), but there was some sort of midrange hollowness I couldn't quite put my finger on, and I wasn't a big fan of the tweeter - I wouldn't say it was harsh, but not smooth either. I still think they're a good value for someone looking for towers on a budget. I found the soundstage and imaging were a bit fussy with position - put the speakers too close and soundstage collapsed in the center, but too far apart and the imaging suffered and the L and R were a bit too easy to localize as individual sources. I couldn't seem to get these just right to find a balance between the two.
The Center was reasonably clear, and generally voices sounded pretty natural. Only occasionally did I notice deep voices sound a tiny bit congested, and sometimes that strange midrange hollowness was there. It didn't "disappear" completely, but did an ok job. Since I didn't demo the Level Two as much as the others, this could have been source material related. Even the NHT TwoC, which I think did the best disappearing act of any center channel I've owned, could draw attention to itself with certain movies/shows.
Mordaunt Short Aviano-1 - At the closeout price, I feel there were the best overall value of the bunch. Solid build and quality sound. They're not entirely neutral, but they are a fun and relaxed listed. The tweeter is smooth, and a little relaxed in presentation compared to the mids and bass, which I tend to like in speakers. Bass is strong - good punch, but a bit too full. They remind me alot of the Energy RC-10, but with a more forward midrange. They share the same drawback I found with the RC-10 - the upper bass/low mid warmth is a bit much in comparison to the rest of the spectrum. However, and I'm only going from memory here, I think the Aviano was cleaner than the RC-10, at least in the lower mids. I think these have the best resolution of the bunch, except for the thickness on the low end. I also think they just sound more refined for lack of a better word.
If I were buying a pair for 2-channel listening, I would take the Aviano over the others. But with HT the main goal here, I found the low end warmth could make voices sound a bit overly full (particularly with Dynamic Volume on), and as a center, the speaker didn't "disappear" well enough, making dialogue seem a bit disconnected from the screen. I did notice when listening in stereo, this speaker did not project a tall soundstage, which might explain why as a center, it didn't do a good job of making it seem as though sound was coming from above the speaker. I think the bumped up lows and bit of midrange push are probably the reason the soundstage seems to sit a bit lower in space.
Cambridge S30 - Revisiting these, I find my opinions from before have not changed much. The bass is really nice for such a small speaker. Clean, but punchy - not as prominent or full sounding as the Aviano. For music, I think one can get away without a sub, but I do prefer a sub in the mix. Again, not entirely neutral - I still notice that upper mid/low treble push, which can make certain vocals seem emphasized, and things like acoustic guitar strings have a bit of extra bite. It can also make the sound a little edgy at times. It's an interesting tonal balance - seems a bit laid back in the treble, but at the same time the low treble/upper mid is forward. Overall though, a nice but lively listen, with good imaging and a wider soundstage than expected for speakers this small, probably on par with the Aviano. The tweeter is not as smooth and clean as the Aviano - sibilance a bit more noticeable... better than the HTD though IMO. I suspect Dennis Murphy's mod that uses a steeper xover slope and suppresses the woofer breakup might actually help with this. Still, a very good bargain for $220 retail, but I think the Aviano is a better deal right now.
HVL-1 - These won't win on appearance for many (including me), but I think they stand alongside the S30 as some of the best values for this retail price range. I think Dave F. and Curtis did a nice job on these and have a winning product here. The cabinets seem a bit more hollow and less solid than the Aviano and HTD, but they are still fairly solidly built - 3/4" MDF or additional bracing would be nice, but not expected for this price. The S30 have much smaller panels, so despite the lower weight, they seem a bit less hollow. The matte vinyl is nicely applied - seams are clean. The dual flares on the ports is a nice addition for this price point (not often seen), as are gold plated binding posted instead of the plastic cap binding posts on the S30.
As for the sound, they seem to follow the Ascend house sound from what I remember from the HTM-200SE. They are pretty balanced, but to my ears a little lean and little bright in the treble... just not as lean/bright as the HTM-200SE. The mids are nice and clean, and while not the best resolution I've heard (think NHT Three, Boston VS260, Ascend Sierra), it's good for the price point. I think the Aviano is a bit better in terms of resolution, but the HVL has a less colored sound - flatter balance to my ears. Still, I wish the tweeter was a little smoother, or perhaps padded down a dB or so.... or maybe both. The low end is very clean, but not much bass weight or punch - a bit leaner than I'd like. These need a sub, even for music.
Not as wide a soundstage as the S30 and Aviano, but taller for sure. I was surprised how well the sound was projected above the speakers. When doing the first comparison with these against the HTD Two Towers, I switched to the HVL and actually wrote down, "Wow, did the soundstage just get bigger?" The soundstage didn't seem to have the same depth as the Aviano and S30, but I wonder if that is due to the not having the obvious push in certain parts of the midrange like they do. Imaging was good too, and the only time I noticed it suffer was with sibilance in vocals - it seemed to momentarily draw attention to the tweeters, which temporarily hurt the imaging. I didn't notice this with the Aviano or S30. It's not that the HVL is a sibilant speaker...but I am very sensitive to sibilance and extremely annoyed by it. With the HVL, if it was there in the source I heard it. The smoother tweeter and relaxed treble of the Aviano make sibilance less sharp to me. I've been trying to determine if the S30 is any better than the HVL in that regard, since I feel it's a bit less bright in the treble, but really don't find much difference.
The thing I like the most about the HVL is that taller soundstage. IMO, this really helps the speaker disappear as a center channel when oriented vertically (which was only temporary for me since it was blocking the bottom bit of my screen). Oriented horizontally, it didn't disappear quite as well, but I'd say was still close to the S30. I didn't notice any obvious off-axis problems using this as a horizontal center, but I didn't spend much time trying to listen far off-axis. With Dynamic Volume on, I notice minimal low end congestion or boom (probably the thing I hate second most to sibilance) with voices, and feel deeper voices sounded cleanest on these speakers - likely due to the lean bass of these to begin with. While they wouldn't be my pick for a music only system, I think they work very well for movies. Don't get me wrong, they sound nice with music too, but not my preferred sonic character for music - I like a more relaxed sound and the Aviano is more to my tastes.