For debian stable you should try my fglrx script for your ati card. And for your nvidia card well maybe backport a new driver yourself or use the nvidia-installer. In case of fglrx you can then use xbmc xvba with xbmc fernet menta (i have got a script for that as well), for nvidia you can use mplayer or xbmc. vlc is possible for both via wrappers but it takes too much cpu load just for output. xvba does not support h264 l5.1 however.