I have a 2011 Mac Mini and I have questions

Right now, I use it solely as a Roon server? Currently it is running Ubuntu 20.04 LTS, with a minimal installation, and the desktop version of HQPlayer that doesn’t work too hard considering I use it to play to a Schiit Yggy that can only do 24/192 anyway. Is there a better version of an Ubuntu based linux I could put on it?

The machine has an i5, 60GB SSD, 16GB of Ram, and the music is on an external HDD. It does its job now comfortably within a degree or two of 60C while playing, and down to 50C when not. Would a larger SSD and some new thermal paste be a worthwhile investment for this machine considering it still functions perfectly?