I have to say that the X5 reviews make the sound sound nearly perfect for my preferences. Neutral with a hint of warmth/musicality/analog-iness. I'm probably going to cave and get it, even though I just got the X3.
Keep in mind that one man's neutral is another man' warm. When I made the neutral comment I had the DX50 in mind, this guy bass is red hot so the X5 is rather neutral compare to it. Have I had a bass light player, then the X5 might have sounded warmer. Now one thing that can add to the sound signature, at least for me, it the burn-in time. I barely crossed the 40 hours burn-in and have already sensed that the bass got extended. That could also appear warmer.