+100 for Equalizer APO.
Awesome program and a must imo for the HE-400. I wouldn't only want to tame the treble in music players, but games and Youtube videos as well. I don't use the program anymore since moving on from the HE-400 but I'd strongly recommend the program to anyone.
I'll have to take a look at that GUI app you posted, looks really helpful. I was editing the config file before to create my EQs which was a pain in the neck!