Yeah, that curve looks incredibly wrong to me--way boosted in the treble. As Adam would say, "There's your problem!"

Also, 5 channel stereo kinda stinks--try using DTS:Neo 6 or Dolby Pro Logic IIx+eXTremeSTiUltra.

That will definitely give you a different sound. I'd also experiment with regular stereo, so you know what you're messing with when you turn on the surround modes.

Do you have your SACD player hooked up over HDMI?

I am the Doctor, and THIS... is my SPOON!