I'd personally try and swing the 51xx xeon, those processors just fly. I replaced an office's dual core 3GH MsSQL server with a dual dual core 5150 server, and the staff was thanking me as soon as the new server when online, and they're still grateful a month later. Queries which used to peak both cores are now blips on the load graph. There's magic in those processors, they're the first ones I've actually cared about from Intel since the Pentium M.

Matthew