Been there done that and was a Bybee dealer.
I still have some in an in line RCA if anyone wants them.

The Bybees alone were $80 and these have Vampire's best ins and outs. I have four of them left and will take $50 each for them. I also have one of the newer Bybee slip stream filters that at the time were $125 each. I'll take $75 for it.
Basically what they are is a high frequency noise filter. With most systems there are some notable effects and with a noisy system the effects can be positive. However, I have found that on top level systems they tend to take away air and space cues and cause the sound stage to flatten out. So I no longer use them anywhere in my system.
The last place I was using them was in the digital out from my transport to my DAC. Here they had some positive effect without any negative. But I am not using a transport anymore either.
Anyone that wants to try these may do so at no cost to see if they are good or not for your system before purchasing them. Another free demo!