I am using a Xonar DX soundcard in conjunction with 668Bs, plugged at the back (heard the front plugs have too powerful amps for my cheapo cans).
As it is, I've been using the following base settings for everything (no EQ or extra effects in other tabs) but... :
...but I don't even really know the capabilities of my cans (not very knowledgeable about sound gear in general), which I bought on friend input. That's my major issue, as I don't even know what would benefit them or not. I don't know what to do when using different sources (music in .flac, videos, games) either, as I should apparently change things around depending on that.
For info I use the latest Foobar2K for music. Also I tried disabling onboard sound but it doesn't seem to make a difference.