If you are planning to use your PC to listen to music, connecting it with an amplifier and hi-fi speakers, you are going to need some applications that will let you handle your collection — from converting audio between various formats, to creating compilations, etc. First of all you need to make sure you get the best possible sound quality. It’s been a long time since I use my PC for music, what follows comes from first hand experience. If you also edit audio (cut, paste, apply effects, etc., you may like to check this post on the best free sound editors).
To give you some idea about my criteria, let me say that I prefer a rather balanced sound, sweet, smooth and clear, with a full body, including all the middle area, natural (not heavy) bass, mild (not harsh) treble.
The Source of Sound
If you use Winamp as your main audio source, you will enjoy a very large collection of plugins extending significantly the functionality of the player. Regarding sound quality itself, you must try a Kernel Streaming Plugin that will let you bypass the OS native mixing system and achieve hi end (bit to bit exact) sound, without any need of extra drivers. Note that this bypass may prove only of a theoretical value with differences not being really audible.
AIMP is a player with a similar layout and great sound quality (wasapi or asio). Check also XMPlay, a convenient hi end free audio player. Yet, I have not found so far a player with the convenience, flexibility and power of Winamp.
VLC Untied is a free program that lets you select one or more files or folders in Windows Explorer and load them to VLC media player instantly using a keyboard shortcut, even removing completely any files that may be already loaded and playing.