Here goes another round since I have updated my machine to a Mac mini (mid 2011) with tuned BauXar Jupity 301 (Japanese site) and RME Babyface USB DAC and since software might've had a few version updates by now with hopefully better audio quality if any.
This is tested under boot camp Windows 7 64 bit and not on a virtualized Windows.
I have tried to turn off any of the equalizer effects that would simply ruin the clarity and accuracy of the source under OS setting and under each software.
I have left out apps that actually didn't sound any competitive from this time around.
Interface : ☆☆☆☆★ I like rich and colorful interface (without clutters) but some people prefer light and fast but you can also customize it deeply. In fact, it has easiest to use interface that also remembers the track you were playing before. (iTunes can't even do that.) This app boots seriously fast.
Support : ☆☆☆☆☆ Don't know what to ask more about output and file format support, it probably has anything through plugins.
Quality : ☆☆☆☆★ The quality is definitely solid. It doesn't seem to add or subtract anything but go natural, though then somehow lacks to sound totally convincing.
Interface : ☆☆☆☆★ While many people like Winamp, I just cannot stand its cluttered interface as well as when loading hundreds or thousands of files, it literally takes ages to load up the tag data... It does have million skins but I think it could use a cleaner and faster "default" skin. Boots fairly fast.
Support : ☆☆☆☆☆ This probably also supports just about anything. There's a plugin package that adds a bunch of missing supported files etc.
Quality : ☆☆☆★★ I would have given it 3.5 stars if a half star character exists but I feel that Foobar sounds clearer than Winamp with ASIO, that's a star less.
Interface : ☆☆☆★★ The interface does not look clean enough with dozens of elements and options except the audio quality is top notch. It can somehow decrease the amount of elements displayed if you try through options though. Kind of boots slow.
Support : ☆☆☆☆★ It seems to support a wide range of file formats but out of the box it only supports WASAPI and ASIO isn't easy if not impossible to use. (I never tried ASIO on 4 beta, it did work on 3 through a winamp plugin that seems to belong to some Japanese web site.)
Quality : ☆☆☆☆☆ Under WASAPI, this makes such a great audio quality. Audio shapes into a smooth sphere that flows into mind... especially at high bit rate audios above CD. It does lose total crispness but it's for the better of the overall quality.
Interface : ☆☆☆★★ It looks organized at first, until it feels simply cluttered and not intuitive with too many options. Boots quite fast.
Support : ☆☆☆☆☆ Last time I tried, it didn't support ALAC by default and had to install some external plugins and a little configuration to get it working, but it seems to support it natively from now on. It supports WASAPI and ASIO as well.
Quality : ☆☆☆☆★ You can definitely feel that it tries to output high quality audio, but it seems to only concentrate about clarity but not overall smoothness. For me, I can see about its clarity being boosted compared to other apps but I feel it's not tuned enough as a total quality of the audio. But some people may just like the way it is.
Interface : ☆☆☆☆☆ Just brilliant. In fact this is the only app I feel that I'm satisfied with the interface, maybe along with Foobar. Rich in information yet not cluttered. The checkboxes on each songs are simply very effective that I wish all other app had... It's not a rocket science nor I doubt it's patented... Boot time is, well, nothing but slow...
Support : ☆☆★★★ It's proprietry, meaning, it only supports what it wants to. No FLAC, no ASIO, and I'm more or less forced to use ALAC just because I like iTunes and have iPhone... It does have WASAPI support, also under 64 bit as of late. (That setting is possible from QuickTime preference in control panel as Windows Audio Session.)
Quality : ☆☆☆☆☆ I know that this is up to a debate that many people say iTunes doesn't sound as good but while I agree that it does not have top notch clarity, the overall quality is well tuned as a whole which makes enjoyable and easy sound.
Interface : ☆☆★★★ I'm not even sorry to say but it does suck =p But it's mainly intended as a video player, so, can't blame about it. At least it does have a playlist that you can use. Loads pretty fast except for the first time when it does some font caching.
Support : ☆☆☆★★ Supported files seem fair, except you must add individual files into the playlist or it won't even recognize ALAC as a playable file by adding folders. No WASAPI, no ASIO. It seems to only support 44.1kHz / 16bit though.
Quality : ☆☆☆☆☆ This player is just scary... good... It doesn't try to wrap the audio up by softening it like MediaMonkey but simply makes it rich. Bass effect is just brilliant and it's not even in WASAPI or ASIO mode. Just make sure to boost the volume slider to max. I wonder who the genius in the mplayer team invented such a great cross platform audio engine... It is just funny how an app which (I assume) is never targetted at audio sensitive users sound just about the best out of them all. Just like this, on OS X, MPlayer OS X Extended sounds just as great as well (And another person backed up my claim too). Now, since it's open source, it's time for someone to make a better audio playback interface (perhaps as iTunes integrated as Amarra, don't know if that's even possible under Windows though) with its engine. Could even be my next hobby project...
Frankly, everytime I try to play a song over MediaMoney, iTunes and SMPlayer, I cannot tell which is best as they all seem good on one point and are all convincing.