There is a derectx host plugin available from the plugin page. You should be able to find quite lot of stuff out on the web.
The purpose of room correction, is to adjust the effects that a room has on the sound. Room correction involves more than one process. Ideally, you want the room prepped accoustically before you start messing around with equalizers, be they linear or parametric.
An "ideal" room should have combination of absorbative and reflective surfaces. I believe an old rule of thumb for the ratio was 1/3 and 2/3 respectivly
After the accoustic environment has been dealt with, equalizers can be used to do the final tweaking to get the frequency response of the audio system and the room as close to flat as possible. You need a spectrum analyzer or a sound pressure level meter , a pink noise source to measure and an equalizer to adjust.
However, most people, except for listeners of classical and jazz, don't like a "flat" room. But, then, that's what your bass and treble controls are for.
There are a couple of good sites for further in depth discussion on this and other audiophile topics which I can't find the links for at the moment. Alex, if you're out there, maybe you could add them.