Here is my Audio/Video setup, it works great for me!
I use the CCCP Codec pack to provide codecs for DirectShow based applications. It also helps remove buggy codec packs and installs a whole bunch of goodies like Haali media splitter and Media Player Classic HC.
I set MPC-HC as the default program for running all media related stuff except for some random things like Winamp specific playlist formats. MPC-HC essentially functions as a kind of "Preview" application for all my media files. And it does the job perfectly. It's lightweight without any extra trash like embedded videos of Steve Jobs talking about how cool he is (this can be important if you're having problems running 1080P h264 rips).
For playing music I use Winamp. It's very powerful and has a ton of skins and plug-ins. Back in the late 90s, it was one of the first programs to popularize the notions of custom skins and plugins. It has a really flexible media library that can be setup in anyway you like (for instance, you can have your top 'source' column divided into two different views; a generic artist/album list view and an album cover view). I also really like Winamp's milkdrop visualization plugin, IMO it's the best one out there. Winamp also has a bunch of really cool skins that offer a lot variety and customization, but are still pretty easy to use.
For tag editing and folder structure management, I use a program called
Mp3tag. This is a very powerful program with which you construct enormously time saving macros. It's highly flexible and you can do all sorts of things with the tags/filenames. It also has a cool feature to grab metadata from sources like Discogs and Amazon which is really good for getting album covers. It can do a bunch of other stuff with playlists and exporting your music list, but I don't use playlists. It supports all common and uncommon tag formats and audio codecs out there. While Winamp's tag editing capabilities are quite developed compared to mainstream applications like Windows Media Player and iTunes, I like to have both an organized tagging system and a logical folder structure for my music, so I use Mp3tag.
If I need to do any transcoding, I use an application called MediaCoder. Again this is a pretty powerful converter program that is still very intuitive. While most of my transcoding consists of converting FLACs into V0 MP3s, MediaCoder is supposed to be able to do lots of other useful stuff like converting random video files into container/codec combinations that play on a specific PMP (Like the PSP) or consoles like PS3/XBOX360. They even have dedicated versions for the PSP so you don't have to mess with the encoder settings.
Finally, I use a program called MediaInfo to find detailed information about the contents of various containers or audio/video files. I kind of wish this program was integrated into Media Player Classic HC, their 'properties' tab is kind of useless.
Summary of my setup:
Audio/Video Preview: Media Player Class HC (With CCCP codec pack)
Audio Library Playback: Winamp
Audio Tagging/Management: Mp3tag
Audio Transcoding: MediaCoder
Media Info: MediaInfo
So I basically use several tool that are specialized for a particular jobs.
Foobar2000 is actually developed by a former developer from Nullsoft; the creators of Winamp. While it can do everything that Winamp can do and more (things like transcoding, I also think foobar's tagging and management features at least approach Mp3tag),* it can be a pain to use. It's highly modular and the default setup could lack things one tends to take for granted when thinking about an mp3 player (this might have been resolved in the newer versions). I guess if you want to take the take to get foobar2000 up and running it should probably do everything you'd want it to do.
* can someone enlighten me about this? How does foobar2000 compare to Mp3Tag in the tagging, filename editing (renaming based on metadata and such), folder structure management and metadata retrieval categories?
I would also look into Songbird. It's supposed to be like a more flexible version of iTunes that lacks Apple's totalitarian control policies. Of the the top of my head, I think they have a cool feature where you can add youtube videos into your multimedia library or something like that.
Peace,
Levictus