I litterally just puchased an AMD Phenon II quad core, 8GB ram, etc, etc.. for the exact same purpose. I just installad the db software on the first node. and running gentoo. my entire box is brand new and cost under 500$. I also had a cheap dual proc pentium 3 with xen and had an entire RAC system running without issue. (iscsi for shared media over openfiler) It doesn't take much.. not exactly the fastest cluster, but it worked for a test.

..to Blue-Ray? (Why not?)