Note 8 sound should be ok. Is your spotify premium? If not then maybe spend that money into premium?
A5 should be good enough, depending where you listening from.

I know someone using a Note 8 who said the SQ is quite bad. If you can, go to an audio shop to test with an external dac/amp yourself I think.

Before buying extra thing, try subscribing Tidal HiFi trial and listen to "Master" quality tracks.
Previously I was ok with Spotify but once I started to notice how bad it is compared to Tidal or my hi res files and CDs, I can't un-notice it again.

Spotify Premium offers at most, MP3 (Lossy Audio) at 320kbp/s while Tidal Hi-Fi allows streaming of Lossless audio at 16bit/44.1kHz (and if I'm not wrong, Tidal Master(MQA) allows up to 24bit/96kHz ). Basically, compressed audio vs lossless audio. Usually, lossy compression will cause the really high frequencies to be lost, and can result in distortion in some cases. In lossless audio, the audio is also compressed but encoded in such a way that no details are lost, which will also result in a bigger file size. Usually, the difference is negligible on lower end audio gear but if the same recording is mastered differently for lossy and lossless audio, then the difference will be much more noticeable. So it comes down to whether or not you feel that the small difference in details is worth it to you and/or you have the necessary audio equipment for the said details.

Putting that aside, the pricing not too bad la bro. I sometimes buy JPop Hi-Res albums and those can easily cost RM100 for a single album.