A wonderful patch just landed in Banshee trunk, revived by Alexander Hixon that adds software equalization support -- the typical 10-band deal with a pre-amp. We had added most of what was necessary for this about 1.5 years ago, but never got around to finishing it. Ivan Zlatev did much of the player engine work at the time and actually started the effort, I did much of the UI work, and Alexander has revived it all for our new codebase in trunk.
Here's the old screenshot of the Equalizer UI designed so long ago -- I still like it very much, though it does need a bit of tweaking still:
That being said, I hate software equalization. I'm reminded of "The Death of High Fidelity", a wonderful and sad article in Rolling Stone from a few weeks ago. Very much worth the read, and be sure to listen to the samples at the end of it.
I'm still very happy that we finally have this beast enabled in Banshee though. Thanks to both Ivan and Andrew, and Gabriel for staying on top of the patch.