Presentation is Too Forward, where to start?

My listening position is about 6 - 8 feet from the speaker plane.

do you have an exact measurement of your listening chair from the speaker plane? 6-8' seems to imply that you move the chair around in that 2' region OR you move as your listening session progresses! OR, are you simply ballparking the number; you never measured it?
8' would be better if you could help it.

One question for you: how high are your ears off the floor? Your speaker is only 33.5" tall per the specifications. What I'm wondering is whether or not the drivers have integrated at your listening position? If they haven't, then you are going to hear a lot more treble/high freq & that'll bite your ears. Hence the suggestion to move back to 8' giving the drivers another 2' to integrate. If you cannot move back, change your chair & get one that makes you sit lower so that your ears get closer to the floor. This is another way to get the drivers to integrate. If you are unwilling to sit lower, you can also raise your speaker - you go down OR your speaker goes up: same difference. Yet another way to assist driver integration is to tilt your speaker back a few degrees. I prefer the 1st 2 options & the 3rd only if you've no other choice.
Stereophile did measurements on your speaker model in 2006 but their measurements are at 50" which makes absolutely no sense at all. Who'd be sitting in a chair with one's ears 50" off the floor?? Looking at Fig 6, I was trying to see if their measuring height was correct. If it was the impulse response would have been a triangle rather than a triangle with a starting glitch. Their measurement of 50" is so far above the speaker that it's very hard to guess how much lower you need to sit. In measurements of some other speakers back in time, such as the Thiels, Stereophile used to adjust their measurement height to get a good impulse response (maybe they cared back then & they now have a GFY attitude today? With people paying them sub-$10 per year for their rag, they probably do!). Anyway Stereophile's measurements are essentially useless for home listening.
http://www.stereophile.com/content/monitor-audio-silver-rs6-loudspeaker-measurements

you're right Onhwy61 - I read it wrong! I went back & re-read it & it says "step response on tweeter axis at 50". My bad!

I sit in an office chair at the lowest setting and I'm 6'5" so my ears are 47" above the floor or a foot above the top of the speaker cabinets.

OMG, that's most likely your problem. You are hearing nothing but high freq.
Just the way drivers are constructed, the acoustical center of a tweeter is more in front of the driver than the acoustical center of a woofer. Hence the sound from the tweeter comes 1st to your ears. That's also one reason you find time-aligned speakers (like Thiel, Meadowlark, Green Mtn Audio) slope their baffles such that the tweeter is physically behind the woofer plane. With your sitting a foot above the height of the speaker the drivers have no chance of integrating.
You need to move much lower so that your ears are about 1" BELOW the midrange woofer. This way the tweeter sound will have the longest path to your ears & the woofers the shortest. It will compensate for the tweeter's acoustical center.
besides a beanbag you might also try those canvas lawn chairs (the ones you take for 'music-in-the-park'). The canvas seat sags once you sit & drops you lower. I've used these canvas lawn chairs successfully.
Since you're so tall, your solution might be 2-fold: seat lower + raise speaker.
Let us know how you fare.....