"Install the only individual codecs you need" = pain in the ass every time you come across a new type of encode and having to configure it and your player (and possible reconfigure your other codecs to work with it).
Personally I just install DivX and then for everything else I use VLC media player. Its cleaner and quicker than messing around with codecs/settings in my opinion
I have never needed video codecs for playback before. Just an audio FLAC codec for Winamp. The only time I require certain codecs is for conversion. I use The KMPlayer. Even when I was on MPC - HC I didn't need codecs.
I use KMPlayer as well. Has awesome compatibility with everything I want to play with it. Great media player with great compatibility for many many file types.
K-Lite Standard Pack is good enough for an average/power user. You can try K-Lite Full Pack for an extreme user.