I have owned the Sony SCD-XA5400ES for a couple years now. A few months ago, I tried a Bryston BDA-2 DAC in my system (connected the Sony to the BDA2 by SPDIF). It was easy to A/B the Sony vs. Sony/BDA2 combo by switching my Bryston BP26 preamp back and forth between inputs. The BDA-2 improved the sound very noticeably. The sound was much fuller/richer, with greater depth, and there was much less harshness to the high end. Maybe the Bryston BDA-2 is more than you were looking to spend, but I think it is fantastic sounding and have never regretted purchasing it. Of course, for SACD playback, I still have to use the Sony connected directly to my preamp.
