As an example, in my system all the files are held on external drives and once chosen are copied for playback on to an internal SSD. This allows for unlimited storage and the size of the "playlist" is only limited by the size of the SSD. It takes a few minutes to set up each time, but one gets used to it.
In my case, the dedicated SSD also contains programs for playback (Jriver and Foobar) and proprietary jitter reduction technology and buffering among some others. However may I suggest that the SQ per se may be better served by looking at the complete audio chain (DAC, Amp and speakers) as fundamentally as you are looking at the source even in upgrading a basic computer-based system.