Stand alone tweeter?

I don't think you can just swap the tweeter without having some knowledge of the crossover design. One common and easy way to "tame" a tweeter is by adding a resistor in series with the tweeter to lower its amplitude. Just be aware that nothing short of trial and error can yield any meaningful results. The easiest approach is to experiment with different off axis listening positions until you find one that suits your taste.

If you have grills for the speakers try placing a small coin sized, single layer, piece of soft tissue paper on the inside of the grill @ the center point of the tweeter.

Sounds dumb, but it's subtle enough to be useful.

The tissue may hold/stick with static electricity alone.

Also, if the tweeters and/or mid-bass drivers have rounded head mounting screws sticking out...

Try placing small self adhesive felt dots on the screw heads.

The small felt dots are also subtle, but can be effective as well.

I'll also mention that I do use two power conditioners in my setup and my speakers don't even have tweeters (just single wide range drivers).

Without the conditioners (one for digital source and the other for amps/preamps/TT) the mids and highs do exhibit glare with some source material (both digital and analog). 

DeKay

@gondo101 
Taking a cue from dekay, I'm reminded of an old, less elegant solution if you don't have grill covers for your Forests.  Try hanging a piece of toilet paper (or two) over the tweeters.  Supposedly an old recording studio trick.  

When the Totem Forest loudspeakers were reviewed in Stereophile the measurements showed a lively lower treble coupled with strong resonant behavior above 20kHz.  You're obviously very sensitive to this.  Your only true solution is to get a different loudspeaker that doesn't have this set of problems.  If that's not a possibility I would suggest you experiment with toe-in, tilt and listener height so that you are not listening directly in the worst axis of the loudspeaker's problem area.

@gondo101 

onhwy61 is exactly right about the S'phile findings.  Lowering slightly by removing the balls and perhaps even trying some toe OUT might be of help.  I also found positioning them closer together (under 7 feet apart) was helpful bringing up the bass.  Stronger bass might better balance the treble.  In one review (Audiophilia?) the writer had commented "pay attention to how Vince B. has them positioned at shows".  Photos of Totem Forests from a show allowed the carpet pattern to be used to determine distance between the speakers. They were a lot closer together than I would have guessed.  I do remember the step chang in bass output (and vocal clarity) that resulted moving them to mirror positioning in that photo.  

Belatedly it occurred to me to ask how old your gear is.  Could this harshness be break in pains for the Forests or any of your other gear??  It took a LONG time for the Forests to start producing meaningful bass in my system.  

By the way, you have some VERY nice gear.