Excessive sibilance and edge....treat room?

My experience has been if you want to achieve natural tonal balance from the mids and up, it HAS to be inherent to your speaker's sound, not a by-product of your room. Do this: sit 4 ft directly in from of your speaker and listen to vocals from a known source. If they sound natural, you're good. If they don't, no amount of room treatment will change that.

I'm pretty sure that you are going to have to fix this with equipment. I'm not familiar with the tweeter that your speaker uses. I've never heard silk dome horn, so I can't comment on it. I do see some potential problems with certain parts of your system. Your CD player is excellent, but they don't call it Resolution Audio for nothing. Its a very detailed CD player and its not forgiving. If you play a bad recording, you will definitely hear the bad and the good equally. Normally, I don't like to recommend cables to fix problems, but your Supra 3.4 Ply is almost certainly not helping any. Its one of the more fast, detailed, bright, etc.. cables you can get. If you can somehow try a different pair of cables, you definitely should. Also, given your amp is only 18 watts, its very possible you are working them too hard. When an amp is straining, it becomes very difficult to listen to. You may have to get something more powerful.

Consider isolating your source. Footers made of cork, rubber, foam, wood what ever works. Diana Krall (The Girl in the Other Room) use to fatigue the heck out of my ears due sibilance. Solved the problem by isolating the cdp.

Also consider isolating the speakers. I had an annoying high end artifact that would surface every now and again and removing the flagstone under my spiked speakers eliminated it completely. Even with 2" maple butcher blocks atop the flagstone, the high end annoyance was still there, to a lesser degree.
That one baffled me.

All the best,
Nonoise

@Zd542 & Larryi & Everyone...wow...a big thank you for all your advise.

While my system is not really edgy per se...it definitely could be smoother and more refined in the top end.

Listening in the nearfield does yield a smoother and fuller sound. Unfortunately...that is not my desired position since I am on the computer all the time while listening to music.

I wouldn't say that my bedroom is live sounding...but when clapping, there is a distinct echo (not long though). That is what I would like to tame and hopefully it would ultimately result in a much smoother and refined top end. Would also like improvement in soundstage and image size...Larger!..:)

I listen to jazz female vocals and jazz instrumental...not loud and my bedroom is smallish...I am hoping that my amps (18 watter monos) have adequate power to drive my speakers...90 at 6 ohms. I can't be sure though.

Would treating the 1st reflection points on the side walls and some kind of diffuser or absortion on the front wall be a step in the right direction? How about that echo? What's the best way to get rid of it?

Thanks.