I would take any comments about Musicality and Speed, Tightness, or other such things (like sealed vs ported) with a serious dose of skepticism.
Modern design practices have turned these old Audiophool Myths on their head. Unfortunately, the Audiophool is very convincing in their arguments to make others think as they do... so these myths persist.
I recently read a thread on another site where a guy insisted that port resonance was this biggest problem he ever encountered and therefore would only use Sealed subs. Somewhere in their he also commented that he ran his subs as high as 750Hz! (Just so we are clear, Subs don't play that high.) His claim is that they had to be run that high in order to integrate properly with his mains using a very shallow crossover.
Nobody in their right mind does this and it was pointed out and elaborated on quite thoroughly. I share this because it is a perfect example of 1 guy giving advice that should never be followed, but at surface level it sounds like it makes perfect sense... especially if you aren't studied in basic design principles. If he had his way, no Subwoofer would exist larger than 12" cones, Sealed, and playing so high they are beaming. He also went on record as not caring to have any performance below the upper 20s.
SMDH.
We are absolutely blessed here at AH to have Shady, an experienced reviewer who is also skilled at accurately measuring Speakers and Subwoofers. While he has to play the review game, his most "controversial" comments are from the peanut gallery complaining about a $2000 Sub being said to have good value!
This is to say, and assure you, that Shady, in my 4 yr experience here at AH, has always been a straight shooter when it comes to advice.
Now, on to your main question:
If you are truly concerned with the CS aspect of owning a product, I think that you should buy from SVS. They are known far and wide for taking great care of their customers. You pay for it, but they deliver.
Arendal is supposed to be a great company, but not being based here in the US I think leaves some question as to how well they will handle problems with their product if they are to arise.
I have never heard of any complaints about Hsu.
The complaints I have heard about Monolith were further back in the past. More specifically, I have heard people say they are now sending out replacement Amps or Drivers to repair in the field if anything goes wrong. I cannot specifically back this up, but have heard it discussed on many occasions.
For the record, this is what SVS does very frequently for warranty service, too... and I've heard of SVS doing this for customers even outside of warranty.
The sad fact will always remain: it is the dissatisfied voice that gets amplified the loudest. Praise is often lost in the surrounding din. We have one member here who damaged their Monolith Amp and Monolith replaced it outright, no questions asked. You don't hear
those stories... but somebody destroys their Subwoofer and gets warranty service denied becomes the news of the century.
You've already received great advice.
Happy hunting!