Sorry to be responding to your question almost a month after you posted it. If you're still looking for information on vst and equalizer plugins, maybe this'll help.
VST plugins, which can include equalizers, reverb, chorus, and whole array of other effects, are typically small .dll files which work within a "host" application -- usually a sequencer for studio work, and usually pricey. There is, however, a good little "donate-ware" vst host available at <
http://www.hermannseib.com/english/vsthost.htm >. It's good for getting a sense of what vst is and can do, but to make it capable of processing the sound from some other program, for example, an mp3 player, requires quite a bit of convolutions with virtual audio cables, etc. Moreover, the host doesn't do much on its own. It needs the vst plugins to be much of anything.
Fortunately, for the purposes you seem to be aiming at, there's a plugin for foobar 0.9.x that turns foobar into a simple vst host. In other words, you can use the foo_dsp_vst plugin to allow you to use vst plugins like eq's, etc., with foobar. It's available here <
http://pelit.koillismaa.fi/plugins/show.php?id=205 >.
Unfortunately, foo_dsp_vst only allows one vst plugin to be used at a time, though, which is fine if all you want is an equalizer. But if you want to add a touch of reverb, or use any of the many other vst effects out there, you need to be able to chain them together. That first vst host I mentioned above does a really nice job of that, allowing you to chain effects both in series and in parallel with one another. But far easier to set up and use is Acon's vst effects chainer, available here <
http://www.acondigital.com/us_effectchainer_features.html >. It acts as a vst effect itself, meaning you can load it into foo_dsp_vst -- but then it allows you to open multiple vst effects within
it, so you can "chain" a delay, chorus, reverb, and eq in series within it.
The one last thing you'll need are the vst plugins themselves. When you go looking for these, you'll find a whole plethora of them available as freeware, even from some of the larger commercial firms. Don't be turned off by them. A lot of the free vst effects are every bit as good as their (sometimes) expensive counterparts. The "classic series" by Kjaerhus Audio is one of the better-known examples, available at <
http://www.kjaerhusaudio.com/classic-series.php >. You'll also find a whole range of equalizers, from the basic to the very sophisticated (well beyond what I used to think of as parametric eq's); but not all of those are free. The basic 31-band eq I like, however, is -- it's available as a free download here <
http://habib.webhost.pl/vst_eq31.php >. And after all, the 31-band is sort of the "standard gear" for most of us for eliminating resonances in loudspeaker/room setups. And it makes a nice arrangement coupled with the Kjaerhus classic reverb running under the effects chainer through the foo_dsp_vst plugin/host.
Just one word of caution: less really is more. (Would that I would heed that advice when posting, no? :) It's very easy to lay one effect on top of another and get caught up in the "that sounds cool ... maybe a little more ..." bug. The effect you want isn't "wow, what cool cgi they used in this movie," but rather, "I felt like I was aboard a real spaceship the whole time." The audio equivalent of that is that someone who's experienced in running sound should have to listen intently to figure out what you've done to shape things, and the casual listener should not "hear" the effect at all, but just think, "gee, that sounds nice," or warm, or rich, or whatever.
Anyway, if you're still looking for a more robust eq than the one built-in to foobar, I hope this helps.