Hey,
I wasn't able to test all three of them, but I managed to check the MM400 and the Focal Classic. They both sounded great in my ears, but the MM400 were the winner for me. Their sound is pretty hard for me to explain. I just coudn't find any major deficiencies. I have tested them with several different genres and they sounded awesome with all of them. They are involving, sound very natural, have good separation, great soundstage etc. Plus, they were really comfortable. I had to re-adjust them when I did several quick movements with my head, though. It's not so bad, but still. My other gripe is that from what I have read so far most 3.5mm audio cables wont fit. Laaaame.
The Focals were pretty good too, mostly flat. The mids sounded a bit "dull" for me? My main gripe with them was that they were really tight ( the employee told me that they get more comfortable after a week or two of regular use).
The audio center I visited didn't have the Oppos. I probably won't buy them though since in my country they are about 40% more expensive than the MM400s. Even in amazon.co.uk the price difference is about the same.
So, I will most likely buy the MM400 when I get my paycheck next month. After that, I will follow your advice and buy Cayin C5 or some other decent amp, since there really was a difference when I plugged them in with only my Fiio X3 (maybe a placebo? Dunno since I am an amateur)
Well, that's it from me. I am aware that this comparison/review was a bit sloppy. Sorry for that. Thanks for your recommendation for amp. Will keep that in mind. BB money in my wallet ;(
PS: Do you think that the M400 will age well? Will they still look good in 2 years or so?