I've recently built a media centre myself with similar requirements.
Passive isn't worth the extra money and effort, when you can get fans such as the nexus 120mm which are inaudible at 7v.
I went for onboard 6150 graphics, all boards with this are passively cooled anyway, and many come with dvi. I then chose an antec nsk2400 which has really good case cooling and i'm currently using the stock cooler for my 3200+ with the fan massively undervolted. The stock fans and psu in the nsk are all very quiet.
I'll soon be upgrading to an xp or si 120 with a nexus/yate loon fan which if undervolted will be silent.
If you need help choosing a board let me know as i spent some time finding the only mAtx 939 board with dvi, hd audio and overclocking options with voltage adjustment, so i know where to look.
Answer these questions and i'll do you a spec if you like. Do you need 5.1 and hd audio? Do you need overclocking options with voltage adjustment? Whats the budget?
Edit: A typical minimum for a decent media center is about £500.