Thank you. I completely agree. That is why I always install the sub last. I build in stages. While I do plan for a sub, my SQ builds have always had the mids and highs completed first. When I'm happy, I add the sub. A quality system without a sub is still very listenable.
Yesterday I experienced a prime example of highs making the mid bass sound better when I replaced the factory paper tweeters in the dash with Dayton Reference 3".
I don't listen at the volumes I used to, so I would be more than satisfied with a sealed 12" whether its an HO or Ultimax. Heck, I could probably get by with a 10" since I was good with a single 8W1 microsub in one of my builds.