Likely culprit for harshness at higher volumes?


I'm a newbie to higher end audio. I have a very modest system:
1) Pre-amp: Anthem AVM2
2) Amp: Adcom GFA-5400
3) Source: Sony CDP-X111ES CD player
4) Speakers: KEF C75
5) Toslink between source and pre-amp; cheap RCA cables from pre-amp to amp; 16 or 18 gauge speaker wire (Radio Shack?)

Room setup (10-ish feet x 20-ish feet rectangle):
1) 2 foot deep cabinets along one wall (20-ish foot)
2) Components stacked on top of small end table against rear wall (10 foot); centered between cabinets and opposite wall.
3) Speakers slightly in front of end table and about 2 feet from side walls and 4 feet from rear wall

Sounds good at about -45 to -25db; but higher frequencies get harsh at higher than -25db.

Appreciate your thoughts.
There are some computer programs like that, but I'm not sure how sophisticated they are. I think real rooms -- sheetrock vs. plaster vs. concrete, suspended floors, alcoves, heating ducts, furniture, doors, hallways, etc -- would pretty much confound the results.
re: Kind of Blue -- Yeah, it's the recording. I have it too. Same issue. My buddy has it in SACD. Next time he comes by, I'll remind him to bring it with him again so we can re-compare.
There are a slew of reasons why the sound gets harsh at higher volumes. Unfortunately, many of the reasons are off of many audiophiles' radar screens. Consequently, addressing the usual suspects such as room anomalies and "mismatched components," while somewhat ameliorating the situation, do not eliminate the harshness.
After sampling Adcom's GFA-5400 and GFA-5500s, I'd say they are the main and most likely culprit. The MOSFET outputs do not like low impedence transients I came to discover. To exacerbate my "harshness" problem, I was driving 4 ohm MBQuart QLS-830s. Once I switched my amps to Adcom's GFA-565s with bipolar outputs the harshness went away. (exposing other problems but I digress)