I've tried a few over the last 18 months.
Quod Libet
Amarok
Foobar 2000
Jriver Media Centre
Audirvana +
Pure Music
Fidelia
Amarra Symphony
Linux didn't play DSD (at the time), so that was out, Foobar I use today for convenience on my work Windows machine, J River wasn't stable, kept crashing at odd times. Audirvana+ is a solid perfomer, plays DSD native and .iso but needs a bit of time to settle down. Fidelia has the worst gui, can't live with super zoom, Pure Music is a standby, excellent quality of the players that work with iTunes.
Go to player of all of the players is Amarra Symphony, clarity, definition together with the robust database in iTunes works. Amarra can get upset at times, but for reasons that are understandable, and it comes good with a bit of hammering and sawing.
Of others not mentioned, Clementine, XBMC didn't output bitperfect to the sample rate of the track, Winamp and WMP were rock bottom for SQ. iTunes on Windows is not an angel, far as sound quality goes, just is lacking. On OSX, different animal. If it changed the sample rate by itself, it is a great standby, especially on Mountain Lion.
For the platforms I found that OSX and Linux have the better SQ compared to Windows, so the choice of player is limited to the OS and your preference for file storage, some are cross platform, JRiver announced a version for OSX in development, but not released as yet. I suppose you could cripple Windows enough so it wouldn't use so many resources it doesn't need to play audio, but it's a lot of work, and there's no gurantees of it working, and it didn't (for me). Jplay I tried, but it crapped out on my notebook a Sony F127.
These statements are all subjective, I'm the only one that listens to them, so I'm happy
