I had the chance to listen to the IE800 today and to my surprise, I actually liked them quite a bit.
Coming from a pair of UM Merlins, I was especially impressed with the treble. Compared to the IE800, the treble of the Merlins sounds a lot more recessed. I'm very sensitive when it comes to treble and to me the IE800 trebles are very smooth with good extension while far from being harsh. But I wish it would have some more "weight" to it though. On certain tracks the treble sounds too thin for me and therefore can come across as a bit unrealistic.
Being a basshead and loving the bass of my Merlins, I was skeptical that the IE800 wouldn't have enough bass for me. Oooohh, was I wrong!
I listened to a variety of HipHop, Pop and EDM tracks and not once did I have the desire for more bass. Extension is nice and low with a slight emphasis on sub-bass. Detail and speed is also good but not quite on par with my Merlins.
Mids are probably one of the nicest I've ever heard. Very refined and clear with lots of details. If I would have to describe them with one word it would be "natural".
Overall, I was very impressed with the IE800. It's once of the most balanced IEMs I've heard with good extension on both ends.
My only two gripes would the that it doesn't have detachable cables and that the trebles are a bit too thin.
Now I'm seriously considering getting a more balanced IEM with a good treble extension to go along with my Merlins.
Any other recommendations?