Depends on the headphone. For my Hifiman, I don't change much, just the sub-bass, because it can handle the bass frequencies becoming stronger and louder without it hurting the gooey, perfect mids that it has. So I equalize out everything and leave a healthy portion of bass, and a tiny touch of sugar on top. I do this for not all music, but for when I just feel like having a sub-bass treat with some electronic music. I do very different EQ's for different moods and different headphones of course. As well as my speakers too.
Here's a quick example of a sub-bass emphasis for my hifiman based on use with a 50 watt speaker amp (see above chain description):
I've not had problems with different equalizers in foobar, but I've read others have had them be buggy or crash or other things. Mine weirdly enough have not. This one is just called "Graphic Equalizer" and I'm using the 20 band version as it suits me. Works great.