Likely culprit for harshness at higher volumes?

Its difficult to know anything by the volume references you have included. Typically, you want to report loudness in decibels (ie. 80-90-100, whatever) via the use of an SPL meter to better report how loud you are talking about. Since you like the Shack, they have them in there for pretty reasonable prices. If at some point you are going to address room issues, having even a moderately good SPL meter is very handy.

Your speakers may or may not be the cause, remember the speaker is conveying all the problems from the source on through to it. Lots of areas to pick things up and be exposed by the speakers at higher volumes.

Do a simple clap test in your room, without music on and listen for the slap echo, etc. . . a lively room will really accentuate such problems. I would do this and then address some reflectivity with items around the house for experimentation (blankets, pillows, speaker location, etc. . .

Good luck and don't start replacing too much until you at least look into the room to some degree, it could save you a fortune and lots of headaches.

Saru, why don't you at least post the city or vicinity you are located. I am sure others may be willing to stop by and listen, diagnose, and even help you ID the problem with bringing some stuff (equip, cables, deflectors, etc. . . ) over.

Any component can create congestion, HF glare, etc. . . as part of a combination with other components (or alone).

I once owned an amp (Theta Dreadnaught II) that was literally unlistenable for me. Nora Jones sounded like the worst singer in the world with that amp, any time her voice reached up it sound like she had a horrible scratchy, distorted voice. This sound only revealed itself when the amp was installed. I replaced the amp and everything went away. I once had the same issue with a DAC and another time with a CDP (but with the CDP it was only at higher volumes where it became apparent - and much less so than with the Dreadnaught).

Your steps seems to be in good order, but try to find people in your area before you start replacing components on a guessing basis. You may replace half your components before you find the real culprit if it really is even component related???

Saru, I suggested earlier and maybe missed it in one of your replies, but why not tell us where you are located. You may be surprised by other people who reside not too distant from you would be willing to help you out a bit.

Sebrof's comments about saturating your room (overdriving) is relavent. Every room will eventually hit a saturation point and performance can/will abruptly change when that happens.

I am still confused by the references to volume, but in particular you have made some statements about when you turn the volume up to painful levels (ie. well beyond your normal listening levels) is when you experience the greatest problems. I think a lot of us don't turn the music up to painful levels or over saturate our rooms. Part of my note on this is, why do you care what your system sounds like at levels well above what you will want to listen to it?

I am in Kalamazoo Michigan. If you reside near me, I would be happy to help you out. I have plenty of extra equipment (digital, preamps, amps, speakers), cables, sound panels.