Unless you work CW, none at all. Maybe for resale value later on but still very little. What those filters do is narrow the pass band of your receiver. On SSB the voice pass band is typically 2.7 Khz. Some may get a narrower pass band say 2.4 or even 2.1 Khz. That will reduce the quality of what you hear, but if there is some one real close to your frequency it will make it so you can talk to the other guy.
CW filters are even narrower than that. I bought a 400 Hz filter just to fill up all the slots in my radio. If I tune some one in when it is real noisy, I can switch to that filter and everything drops out but him. His S level drops a lot too. I don’t use CW but just had to have all the options for my radio.
There is an old cold war story about a spy using CW a Khz or 2 away from the carrier frequency on Voice of USSR or what ever the propaganda AM broadcast station was back then. He was using 100 watts on CW, the AM broadcast was using several KW and by using the mechanical filters on a Collins receiver, they were able to copy his messages and was not detected by the local authorities. Not sure if that is true or not, but that’s the rumor around the dark com world.
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