I too am very sensitive to HF. While this may have something to do with our relatively 'virgin' hearing, it also has to do with personal taste of musical presentation. The HE90's to ME are the best headphones bar none. BUT, and this is a big BUT (
), it took a while to get to the point where the HF was controlled yet extended, the bass deep and punchy yet articulate, the midrange smooth yet involving, the transients handled correctly with speed yet still realistic with proper handling of the sibilance (Especially the sibilance), etc... etc... Know full well your HE90's aren't performing well if you are noticing too much sibilance (this even bears true on relatively poor recordings with unbalanced HF). I spent a lot of money getting it right (READ: Scrooge McQuack style dough), and now I believe I have the best headphone system in existence. :0 (I Accept all and ANY Challengers, lol!)
There are two scenarios for the HE90 IMHO - a relatively unresolving setup that brings out the euphonic character of the headphone. This will have a more blurred and 'darker' presentation (comparatively speaking), but it will sound great and very smooth.
The other solution is to get these headphones to reach their peak. This means upgrading to an amazing source/DAC combo, good cables, power rengerator, whatever... it depends on individual circumstances. But the thing is, going this route will be superior in every way ONLY as an end result. It is actually far worse when this scenario is incomplete because these headphones will clearly show you what components are not performing up to par.
Before the HE90's I was not a believer (or a strong beliver) in good inteconnects & power cords. Am I now? Yes, absolutely. I have a pretty good HD6X0 balanced rig. It is not nearly as sensitive, and I can see my old tastes and biases holding true with this system. But certainly not with the VD (IC & PC) connected EMM Labs CDSD/DCC2 (w/Optimus EMM Glass Fiberoptic IC Between DAC/CDP) -> HE90/HEV90/ES-1. I presume the Aristeaus will be in a similar class.
Just my .39 cents.