I've charted Geekbench results gathered from the Geekbench Browser for the following Macs: iMac (Late 2012), iMac (Mid 2011), Mac mini (Late 2012), Mac Pro (Mid 2012), and Mac Pro (Mid 2010).
Take a look at the chart below...
New iMac vs Old iMac
New iMac vs Mac mini
New iMac vs Mac Pro