Since the new Mini and iMacs now use Socket P, it looks like it might be possible to upgrade them to quad core (assuming the processors aren't soldered in). Suitable processors would be Q9000 2.0GHz, Q9100 2.26GHz and QX9300 2.53GHz. I know this isn't really necessary for most people but I thought the idea of having a machine about as powerful as the first gen Mac Pro in a machine the size of a Mini is quite impressive. So for ~£1k, one could have a Mac Mini with 4 cores and 4GB of RAM. The Mini can also now drive a 30" ACD with the adapter.