I recommend looking at some of the desktop computers that a manufactured by Acer, they are good quality for what you are getting. For example I got an AMD Quad core, 2 gigs of ram and a 320gb hard drive (Perfect for your music and films) for under £400 (About 700USD I think). The graphics card in it is integrated although it is one of the best chipsets on the market and can play games like call of duty 4. It even come with a 19'' LCD.
Have a look at THIS
, that is the computer I have and it runs great.
$535 on that ebay item I sent you, do a little research and find other good deals. Consider building your own computer.