graphic cards-HD video-hdmi...whats the best set up?

Hi everybody, Im new around here and have some questions that i would like to explore to gain more knowledge and enjoy more the computer experience, Im a fan of PCs (and electronic devices) though thats just it, a mere fan, not some super duper highend tekkie geek, so bera with me if some of my questions are "silly"; I just imagine things and want to check if they have been explored, considered or if are practical.....well........enough intro. Lets get started

Im curious about the performance of the PC as media center I mean CENTRAL MULTIMEDIA CENTER for my home, I own and use some old hardware, but still I enjoy it and thus have "experienced" the PC media center experience, via my ati all in wonder mainly, dont watch much tv nowadays but (here is the "but" ) daydreaming about upgrading, getting a new rigg; I wonder about the advent of HD TV, Blue Ray vs HD-DVD, scalr video decompression, fps, herz refresh rate and this kind of things for a HD experience, and how could I achieve a great rigg to experience this. I mean for common applications theres not much trouble and yes I like to play games (not a ultra hardcore gamer mind you) with great graphics and performance but considering how I like to watch dvds, mpegs, avis and other media as well as thinking about the chance to watch HD content, i want to hear your opinions on how to achieve this.
Aside of a great monitor, what graphic card would be best suited for the task? is HDMI the only/best option? how can i get high quality sound if the audio would be directed to the graphic card? This and other questions arise in my mind, but for the moment I want to read your comments on these issues.

Thanks in advance.

The best ideal MediaPC would be a quite one and having it to play games with good graphics means that it will more likely to need a good graphics card. In turn warm components needs more cooling and produces more noise.