I have found that most of the lesser expensive in-ceiling speakers sound very similar to each other. I'm not sure of the directionality of the angled in ceiling speakers, but I'm not for a bit of directionality to the speakers. I have compared Sonance, Polk, B&W, Monoprice, and some other brands, and at the end of the day, I didn't find the audio differences to be night and day between any of them. There were some higher end Sonance speakers I used that did sound better, but they were also a lot more expensive. The 8" Monoprice speakers are every bit as good as the Klipsch or Polk 8" speakers for sure, and should be a fair bit less money overall, which just makes good financial sense.
I would think any speaker with a sealed back box has the potential for better sound, but I would bet that it may be more than most are willing to spend.