Many here, including myself, use digital parametric EQ. It can make a drastic improvement. There are a number of ways to do this in both software and hardware depending on your setup. Schiit makes a few Loki analog EQ products that are well regarded. See link below.
Since “EQ” is too short for a search term here you’ll have to search for things like “software EQ”, “parametric EQ”, etc. Here are a few links you can start with: