I mostly use the Show 8 for playing Spotify and it's superb at this.
I also have an Echo Show 5. I pre-ordered the Echo Show 8 because I heard it's sound was much better. I've been really impressed with it - the sound really is so much better than the Show 5, plus I haven't encountered the fuzzy/static sound problem I continuously get on the Show 5. The sound quality is more than enough for the room I have it in. I feel that even just using it as a music player it was great value for the pre-order price.
The only gripe I have with it is that you can't have the screen display similar to the Show 5. I love the large alarm clock look and the decorated backgrounds on the Show 5. If I could choose to display a large alarm clock on the Show 8, rather than the tiny clock in the corner, I'd be very happy.