That's the filter I had tried as well, I never even bothered with the others since most people said they couldn't notice the difference either. I completely glossed over that setting, I'll play around with that and see if it helps. Yeah that's the main reason I'm hesitant to switch to any other DAC/amp, as I started out with a BTR5 and my god the app was so frustrating to use. Most of the time it wouldn't connect and if it did the settings wouldn't apply when they were changed; the number of times I had to reset that app was ridiculous. I'd rather have a DAC with no app like the G5 than one with a crappy app and as much as the BTR7 and BTR15 look like excellent hardware I don't think Fiio has put enough time into their software to resolve the serious issues I had. But if I can work around some of the issues with the 5K I would much rather stick with it.
Sorry for getting so serious earlier lol, glad to hear you're taking time for yourself.
You could also try to do a steep notch in frequency somewhere in between 6000 and 10000hz. The reasoning being, that this is what the frequency response arriving at our ears is like in real life. The notch in frequency response defines the height perception. Lower Hz notch frequency --> you look down on the stage. Higher Hz notch frequency you look up towards the stage.
Try it with a steep parametric eq filter with a q of 6 and minus 10db.
Listen to music that you love , is well recorded and you know inside out. Probably a good live recording.
Try lets say 5500hz first, let your ears adjust to it for a bit, you will probably then feel like you are in a theater looking down on the musical act. Then switch to lets say 10000hz. It will sound weird directly after switching! However after some time you might feel like being on the floor looking up to the stage. Somewhere in between you should feel like the musical act is playing straight in front of you. Ideally you will now perceive greater height and depth in the soundstage, compared to playback with the filter deactivated. Try it with some other music now, to "validate" the result.
After that you can back off the filter to around -5 or -6 db, as to not reduce the treble too much. I personally get the best frontal localization and height perception at 7000hz. With a filter of -6db and a q of 5.5 there is not a huge difference in treble, exept for the sound being more natural for me.
It must be noted, that for you the "center" frequency might be at a different location , say 8500 hz. This is individual to our personal hearing.
An added bonus is, that you will probably get rid of any sibilance you have been experiencing before. Have you ever heard sibilance when someone was standing in front of you talking to you? No, right? Headphones can never give us correct frontal and height perception, because they don't have a dip in frequency response. They give us treble energy, where there should not be any. Some have a dip in frequency response, for instance the HD800s. It is said to have great staging - I don't know it though, as it is prohibitively expensive for me. Attached a screenshot of hrtf (head related transfer function) for a person at -30°, 0 and 30 in vertical plane. Notice the depth of the dip at 0°(full front)!