It really does make a huge difference. You can have $60,000 speakers, but with no room treatment you won't be getting the full experience. Flipped, you could have a low-medium end setup, and can potentially sound better than a super hifi system with no treatment.
This was my old basement where I started building these. I've made 4 in total now. Made better than anything you could buy. I should sell these
Extremely strudy and do a great job. I will do a full post on how to build these when I have the time. If you lookup the properties of this Safe n' Sound, it's absolutely amazing. It supresses 90%+ of high frequencies, and does a pretty good job of squelching the mids to lows too, especially compared to other materials readily available.