try putting up acoustic panels or some curtains up to absorb some of the high end.
and maybe calibrate your speakers, usually alot of this can be controlled by acoustics traps
do a search on Bass traps or Acoustic panelling. If you are a serious HT person try readyacoustics.com. There is alot of info on this subject on audiohalics and hometheatershack regarding this subject. Maybe in stead of a EQ which if anything you shoulod not even need, but get an analyser and check out the frequencies in your room and hook a parametric eq up. So you can flatten out the runaway frequencies in your room