I suggest you contact Stewart at Sanctuary of Sound in WA state. He is an A'goN featured dealer and authorized dealer for all three of these products.
I asked this exact same question of him a few months ago, and had to decide if I wanted to put the bucks into a great uni player or even GREATER CD-only player. After talking with Stewart in length, I bought the Mephisto II.X. It is now broken-in, and I could not ask for a better product. I consider it the jewel of my system. The II.X is certainly the Mephi model to go for due to the custom-made transport and Anagram DAC II 24/192 upsampler. It totally erases the criticisms of its predecessor models - laid-back dynamics and mildly light on bass. The II.X has such a balanced presentation that I honestly couldn't tell you it has any obvious strength or weakness.
Having said that, the Teac is a superb uni player. The EMC ain't no joke either. Both of these tend to have leaner, more analytical sonics then the AM. This whole audiophile game is about synergy, so YOUR system may work better with one or the other. In my system, the Mephi is the best of the bunch for what I was looking for.
Now if it could only play DVD's & SACD's .... Hmmmmm.....