How to improve video rendering quality in MPlayer

MPlayer has lots options for video rendering and filtering. Any suggestions on good MPlayer options that improve video rendering quality nicely?

My ~/.mplayer/config is as follows with 2 profiles:

[fast]
vf=eq2

[default]
vf=hqdn3d 
vo=gl:yuv=3:lscale=5:cscale=5
ao=pulse

The default one gives good video quality by using the hqdn3d video filter while the CPU usage is high. If the CPU is not enough for some high-resolution videos, the fast profile can be used by calling mplayer -profile fast video.mp4 which will then use the less CPU consuming eq2 video filter.