Sorry about your loss.
It sounds to me that your main input is turntable? If so, can you hook up another source, as an experiment?
You most likely have a cell phone. Spotify lets your stream music at CD quality. Getting the spotify signal into your stereo, could be tricky. You can hook up a PC with the output from a sound card to your stereo. Maybe your PC has a CD drive?
A pawn shop type of outlet lets will sell a Blu Ray player or CD player for less than $100. Blu Ray and DVD players will play CD's. Try one of those as a source, to see if the sound quality changes, for the better?
Just throwing ideas out there. See if a different source makes a difference. If the sound stays the same, it points towards the amp / speaker combo.

