Digital Audio Player


I have a FiiO X5 digital audio player. I hook up to my home hifi system through the Bryston SP3 preamp and then to the Mark Levinson 333. It sounds OK but my question is will a DAC necessary? If yes which DAC is suitable and if not what are your recommendations.
128x128kulaiboy
See here for an in depth test: http://marlene-d.blogspot.nl/2015/06/review-fiio-x5-loaned-by-fiio.html
Pretty good, therefore. You might just possibly hear an improvement with an external DAC, but it would have to be a rather good one like a Benchmark DAC3.