I have not, so I can't say anything about them in comparison to one another. What I can say though is that even eyes closed and focusing hard I can't figure out where anything sounds like it's been lost. Maybe if I heard the IE800s a few more details would pop out at the top that I didn't have before, but then I'd lose that bass and I'd rather not trade bass I can feel for treble detail I can't. But again, that's largely thanks to musical tastes, or possibly a touch of hearing loss at the tippity top end of the spectrum thanks to years of metal concerts.
I've said it before that I'd rather feel like I'm listening at the front row than the back of the hall, which is a big factor in my opinion of these things. They sound like I'm hugging the amplifiers and man I just ADORE it, though I've got a feeling if I was hunting for expansive and roomy I'd be left wanting. I know some people have said these have a big soundstage, but (and this could easily be my stupid ears) I don't think they sound particularly "big". They sound "full" and I can locate each instrument clearly (which is really "imagining" rather than soundstage), but they don't sound far apart.
The se 846's i found when listening does bring you forward to the stage and i wouldn't say it is a bad sound overal (as we said down to taste), but for me they are not as musical as the ie 800's, I compared between both iem's for a good 30 mins to make any sort of judgement. I think it would be awesome if you can try a pair of ie 800's and report back with what you think. Its funny its as if my hearing was condensed/closed when i listened to the se 846 for soundstage, Going back to ie 800 was just airy and open, the Vintage switch on the Hifiman HM901 definitely contributes to this - sounds lovely, so which portable player your using will factor in aswell.