I'm sort of planning on pairing the DX90 up with the new upcoming 400i. I thought about the 560, but I think I'll always be wondering about attaching a seperate amp to juice it. To avoid the dilemma altogether I think I might go with the 400i if the revews are just as good as the 560. If not then I'm back on the 560 train.
I stopped burning in my DX90 at about the 200 hour mark. I just got lazy and the unit sounded so good that I decided I would enjoy the rest of the improvements slowly. I think they're mighty impressive even at half the recommended burn-in and definitely an improvement over when they were brand new (raw). IMHO Only.