Okay. I *definitely* wouldn't spend ten-k on speakers and then put them in those two positions in that room. :-)
I know this is way, way, wayyyy off the topic of what you originally asked, but those two positions, in that room, aren't going to work particularly well for much of anything. But despair not, especially if taking the grilles off helped. (By the way, did you break one? Everyone always does when handling A-P grilles -- the guy who designed them should be shot.)
I think you should reposition the layout of the listening chair and the speakers if at all practicable, so that the speakers aren't in front of furniture. The reason isn't the furniture itself, it's the inability to put any kind of acoustic treatment behind the speakers. If, say, the Sparks were in front of "bare" corners, you could greatly improve your sound with a couple of hundred dollars with of acoustic treatments, either d-i-y or mail-order from someplace like GIK Acoustics.
Failing that, suggestion number two is to do some room treatments anyway. I'll bet that if you slap your hands (hard) in the dead-center of that room, you can hear a ringing sound that goes on for several seconds afterward. Clean, liquidy highs -- especially stringed instrument highs -- ain't gonna happen if they have to swim upstream through that nonsense. For a fraction of your original budget for speakers, you could kit-out that entire room in GIK stuff, maybe even hire the whole thing out if you didn't want to mess with it.
Third, if after all of that the Sparks *still* sound too laid-back at the top (and I think they do, anyway, so it wouldn't surprise me), *then* the best speaker choices for you are going to be nearfield monitors, with or without a sub (probably without, at least to begin with).
Personally I'm partial to the Joseph Audio RM7, the Tyler Acoustics Taylo Reference, or the DeVore Gibbon 3, but that's because I've got limited power. You, on the other hand, could try Vienna Acoustics, Totem One, or even the Linn Katans, which get beaten up a lot in these forums but are in my view a terrific little speaker when matched with good power and good sources. The Reference 3A MM deCapo is highly regarded in some circles, others think the tweeter is fatiguing. Your advantage is that neither price nor associated equipment are holding you back.
Hope all of this helps more than it hurts. But the main thing: don't go parkin' a pair of Wilson Duetta's in front of a desk. You won't be happy with the return on your investment, imho.