Well, true to my own dictum to give it at least a year, now it's been 3.
I've bee using the Furutech GTX-D ® for the past 2 1/1 years. Due to needing another dedicated outlet, I put in the Synergistic and had the electrician come over. After he finished, I listened to the the music with just an integrated amp plugged in to the Teslaplex SE. While the sound was dynamic and exciting (and it had better low-level detail than the Furutech I lated installed), I have to agree that its upper midrange and treble are exaggerated (bright and edgy). Simply unplugging the power cord from the wall and plugging it in to a PS Audio Power Plant lessened the brightness, and this brightness persists, no matter what music was playing, unless it was say, Blood, Sweat and Tears, a pop CD with a slightly muted upper end, for which the Teslaplex SE compensated, providing a more "brilliant" upper midrange. But on Mercurys - and even RCAs made in Boston Symphony Hall, which is NEVER bright when hearing music in it - the sound is a bit edgy. An "Enjoy the Music" review of several years ago also found the Teslaplex to be "crisp" in the upper mids and treble.
My only problem with the Furutech is that it slightly masks low-level detail and while it has dynamics, it does not do it in "0-60mph". It sounds just a bit more slow off the mark, like 0-45. And I have two of them, so it's not sample-to-sample variation. I was surprised, but then, it may be that the Synergistic hypes the detail along with subtle information. I'll have to put in a Maestro or some other outlet to test that out. For now, just posting.