For a couple weeks now I've been using a Datong FL3 active filter I bought from a silent key sale. Its unreal how much of a difference it makes. I was expecting a slight improvement on CW since I don't have a narrow crystal filter, but it's such a significant difference it feels like I have a new radio. Combined with my radios internal DSP, I'm picking out signals I would never hear otherwise. Turn it on and everything goes dead quiet except for the CW sidetone. The filters are 12 pole that come out to something like 70db with very sharp skirts. I'm surprised filtering on the AF side is so effective.... I've mostly just focused on the IF filter chain before this.
The analog filtering sounds warmer and less fatiguing than most DSP gear I've heard, especially with CW sidetones, its almost musical. But I suppose there really isn't a market for AF filtering like this unless you're running an older rig and want to avoid the cost of crystal filters.
I was going to replace the caps considering they're approaching 50 years old. But they all looked fine and its working so well I'm just going to put the new caps on the back burner.