Axiom Home Page Forums General Discussion Stereo Axioms detailed? Sibilant?

What I do get in my basement is occasional "peaking" of a specific frequency at loud volumes. This usual happens on the high end of the scale during a guitar solo. I like the high end being detailed on the M60s but this little issue means having to limit the volume. I have tried to find the specific freqency range with the Denon 3805 parametric equalizer but no luck so far.

I know this is probably a room issue, but I have lot's of furniture in there including bookcases, couches etc and I'm not ready to spend hundreds on room treatments.

Any thoughts on possible cures guys???