Hi Suramu
There are many plugins (or I should say 'components') for Quicktime. They add support for various codecs, like divx or wmv, or enhance Quicktimes functionality.
Check:
http://www.apple.com/quicktime/resource ... nents.html
Quicktime is a quite good, stabile player, but only if its about codecs natively supported by Apple (like h.264). If You are looking for some universal, flexible solution for media playback on OS X , I think VLC is the best. VLC can playback many formats, that Quicktime will never fully support (even via plugins).
For exaple: If you want to watch some movies with multiple audio tracks and subtitles, forget about Quicktime...
I hope it will help You