I installed Music Player Daemon on my device and controlled it with my own client CuteMPC (https://garage.maemo.org/projects/cutempc/) and the total CPU usage was about 10% lower (and memory usage also a few MB less) than with the original player. There was some problems with sound (mutes every now and then), but I think that might be because I have something wrong with MPD configuration (wrong audio device or something).