I'm building a new computer with HT interaction in mind. I've read suggestions here on sound cards and most of them tend to be external cards. When I read articles on building your own entertainment or dual purposes PC they use internal sound cards. Are there advantages/disadvantages to either?

At the moment I don't have a real DVD player, I just use my xbox. Is anyone using their PC as their DVD player? When you do that do you need a graphics or tv card?