Alternative to WMP for media (mplayer?)

Question

I am developing a c sharp app that needs to handle pretty massive MPEG-2 files (6G+) and the windows media player component doesn't play too well with seeking and loading. Fast seeking and loading is pretty important (see: paramount).
I know vlc/mplayer play these files very suitably, but i have been having a nightmare trying to find either good api documentation or a decent wrapper for either.
I read about DirectX's Audio/Video support. Does anyone know if it uses the same libraries as WMP or is it totally seperate? If it is a completely different beast where do i stand with codecs incase someone comes along with some obscure format they have thewmp codec for but not for DX?

Many thanks in advance!!!

Ben