Looking for enough cores to start seeing complex behavior? Check out this Intel Core 2 Quad Q6600 Acer Aspire from CompUSA for \\(750 (sheesh, the *chip* goes for about \\)580!).
Or, if you're rolling in the dough, CNet quite \<a href="http://www.cnn.com/2007/TECH/ptech/07/17/hp.pavilion.mc/index.html"" target="_blank" rel="noopener noreferrer">likes the HP Pavilion Media Center TV m8120n, which will set you back \~\$1200. It comes with a cheap graphics card, but sounds like a good media server.