Non-Gaming Video Card Help Needed

I intend to use my home office computer to conduit video and audio content to my home entertainment system. I have a 46" LEd flat screen TV and high end surround system. I need to add an HDMI card to my Dell 531s. I'm a little lost on the specs for all the potential upgrade cards. If I'm not going to do ANY gaming and my sole concern is the thruput of video and audio of music, videos, TV and movies does DDR2 vs 3 vs 5 have any meaning for my purposes. Likewise the amount of card memory? And Memory interface BUS?
Any recomendations for a low profile card that will support excellent HD and sound? Hopefully silent.