For what it's worth, I've owned the Arx A1b, demo'd the HTD Level 3 bookshelf and Wave Crest HVL-1, and currently own the RBH/EMP R5Bi...
Note that I had them all at different times, so I could not do any proper side by side comparisons. That being said, there are characteristics of each that I recall liking/disliking...
My opinion is that the Arx is the best sounding speaker. It's not perfect, but I didn't find it lacking anything in particular in terms of sound. The main gripes I had with it were the aesthetics and the relatively low sensitivity (by it's not really far off from others in this category). I did not find the midrange lacking at all, and overall thought the sound was very well balanced, with good clarity and openness. The bass extension and quality is impressive. While not a looker, it is solidly built. I had them in my main room for awhile and really enjoyed them.
I liked the Wave Crest, and do think the midrange is it's best attribute.... but, I found the bass lean and the tweeter just a touch forward for my liking. It reminded me of a slightly less bright and slightly fuller sounding Ascend HTM-200SE. The Ascend house sound is there... I did a comparison of it vs. the Cambridge Audio S30, HTD Level Two tower, Mordaunt Short Aviano 1, and Boston Acoustics A25 - so more detailed thoughts can be found here:
http://www.avsforum.com/forum/89-sp...-1-mordaunt-short-aviano-1-htd-level-two.html
I remember less about the HTD Level 3, which is odd because I just demo'd it a couple months ago. It really just didn't stand out for me. I do remember not really liking the tweeter - I thought it was a little hissy, for lack of a better word. I can't say much else about it. It wasn't an off putting speaker, just didn't really do it for me either. Of course, it was well built and the ebony veneer is nice looking - I'd say the nicest looking of the bunch. Another plus is that it's the most sensitive of this bunch, so less amp power need to get the volume up.
The R5Bi is a nice little speaker, and one I will likely keep around, due to the combination of looks, sound, and price... although I wouldn't use them in my main room (13x21x9). I like the red burl, even though it's laminate. I also like the look of curved cabinets over something plain and boxy like the Arx and Wave Crest. The cabinets are a bit lightweight though... but at least being curved helps with resonance control. Sound wise, the midrange is nice for sure, and I agree with the general consensus that the highs are a bit laid back... which to me is a plus. They don't have much in the way of low end though, and have relatively low sensitivity as well (but again, so do the Arx and Wave Crest, and not atypical for this class of speaker).
I'd really be interested in comparing them to the Wave Crest, since both seem to go for midrange purity instead of asking the woofer to make bass it can't. Without comparing them head-to-head I can't say which I think has better mids, but if I had to guess, I'd probably prefer the RBH/EMP due to the slightly relaxed high end. I also think they look alot nice, so I'm sure that would add some bias.
Just one guy's opinions (and with regard to the Arx, it differs from the opinion of the guy in the video who compared the Arx vs Wave Crest)...