I've been impressed with the X3. My gripes are pretty much all design/function related. Sound-wise, I find no real, court-admissable faults at all with it. I finally published my full review of it today after getting a few headphones properly compared. At the price it is sold at abroad, amazing deal. Truly amazing. I'm excited to see where Fiio takes this series and hope to see a much better control layout.
But I don't think there is a player that truly tops the X3 for features/price/size. Yes, you get a number of 'betters' in the top end HM series and top DX series' players, but in terms of raw performance, the X3 isn't touched by its direct price bracket competition.