The A-pillar trim is a bear to take off, the two stage clips that release for the airbags are exactly zero fun. It feels like you're going to break something, and you will if you don't have a look in there to see exactly what you're yanking on. Really long needle nose pliers would be helpful. The shop manual says always replace the clips, and you should, good that they're cheap.
I first installed the Helix system with stock speakers. Made a big improvement, money well spent. I did eventually replace the front door speakers and that made a difference as well, more noticeable at louder volumes though. I did not replace the tweeters though. In retrospect I had the perfect chance when I replaced A-pillar trims but it's such a pain that I'm not going to remove them to replace them now, haha.