Not much really unless you have alot of VHS tapes laying around you want to listen to in 5.1 or you have a gamecube which also uses Doly prologic II. Other then that All DVD's come in Dolby Digital or DTS which the Outlaw does really well so your not missing much unless you MUST listen to stereo recordings in 5.1 beside pro-logic II doesn't even accurately produce "true" 5.1 from stereo recordings anyways.