An untamed room and a vivid speaker...

I ordered the Zu Omen DW Mk II in February and I've been working with it for about two months after the sets arrive in March. I've run it with two solid-state and one tube amp.

The room is difficult: 

A 46" high, by 71" wide window on the NORTH side

A 7'10" wide triple glass set of closet doors on the WEST side, reaching almost halfway along the wall. 

A fireplace on the EAST wall. 

I have one speaker on each side of the fireplace. 

The ceiling slopes up from the fireplace wall, from 8' to 10.5' on the WEST wall. Gerrit at Zu explained that the ceiling is probably adding a bit of a horn effect to the setup. 

The experience is that piano notes and vocals have much too much edge/glare, making the speaker impossible to comfortably listen to for more than a short time. Actually, I can hear the notes sparking my nerves fairly quickly.

My old Klipsch bookshelf speakers, placed carefully on top of the Zu's have some of this glare, but not nearly as much.

My experiments:

I have covered the opening of the fireplace with a thick blanket. I've placed inexpensive sound insulation panels (these are insulfoam type pieces I bought at the home depot)) behind the speakers. I've played with toe-in, moving them from directly facing the listening to position to straightforward. 

Right now, I've got an old twin mattress up against the middle door of the closet. I've got the left side of the closet exposed so the sound is directed into the clothing. So, there is maybe a two-foot section of the exposed glass door leading into the northwest corner.

I'm just trying to see if I can do anything to cut the glare. I have had very little success. Any ideas?

Thanks in advance!