Well I found a place to listen to the 1840's. I was pretty impressed, but not blown away. Honestly the 650's were so impressive. The 1840's were very clear but I lacked that "full of music in my head" experience the 650's got me. In the Celine Dion song River Deep, Mountain High where in the 650's I heard backup singers I didn't know were present on that track, and they were clear and visible, on the 1840's they were present but muffled and muted. Josh Groban - You are Loved is a song I always get goosebumps with, but listening to it on the 1840's left me cold. I could hear everything, but it didn't feel ... "together". It was like eating one of those deconstructed food things that chefs like do to. All the ingredients were there, but it's the sum of the parts which gives you the experience.
The only thing I am not sure about, is whether the Shures would have sounded better not off my iPod (320kbps music) and with a $2000 Amp. like the 650's were connected to. Since I had no ability to test I won't ever know.
Also a new pair of HD650's are about $700 here and the 1840's were $999
The 650's are now ordered and should be here in a week or so.