Yeah I was gonna build one and get rid of my cube but I was like, naaah. I put the dual chip and bumped my RAM up to a gig. Here is the link for the dual chips. http://www.powerlogix.com/products2/pricing/index.html
I have the dual 800Mhz. Thing is sick if you run Yellow Dog or OS X. It's all my little cube can handle without putting a huge fan in it.