Less than stellar recordings you can make better using for example the Charter Oaks PEQ-1. Would not live without it. An amazing piece of gear IMHO.
And the biggest influence on sound quality is...
The quality of the recording itself.
Then the room, the setup, the speakers, and lastly the front end.
I've got recordings that make my system sound horrible, and I've got recordings that make my system sound absolutely wonderful.
None of the gear changes have had that much impact on sound quality.