FWIW, I have received a GB score nearly as good as my friend's 2012 cMP. Better in single thread, and a little worse in multithread. We have x5680s in our system. He has 2 and I have 1.
I have GB scores on my late 2013 MBP that exceed what I get on my cMP. But in real video work, the cMP is much faster and more capable.