So I was just using mplayer -vo vdpau... and here's my cpu util:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
6172 XXX 20 0 155m 50m 14m R 22.9 2.5 0:06.86 mplayer
Thats when I stumbled upon this ArchLinux Wiki post, and added these to my ~/.mplayer/config file:
vo=vdpau, vc=ffh264vdpau,ffmpeg12vdpau,ffodivxvdpau,ffwmv3vdpau,ffvc1vdpau,
And now,
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
6397 XXX 20 0 157m 51m 15m S 2.3 2.6 0:03.73 mplayer
my %cpu dropped from 22.9% to 2.3%..! Amazing, isn't it?