Quadcore or Dual QuadCore?

"Get the memory. 'As a DBA' you're going to be doing I/O bound work more than CPU bound work. Assuming you have a 64-bit O/S the memory is probably more useful than the CPU cores.

If you are feeling flush, get some internal disks (SSDs for the particularly well heeled) so you can test stuff locally on the machine. I use XW9300s (pimped somewhat by adding internal SCSI disk arrays) for data warehouse development work with Windows XP and SQL Server developer edition. This works surprisingly well. A 64-bit build with 12GB of RAM would be even better, and a similar trick could be done with Linux and Oracle."

I would pick RAM over cores. Most programs aren't designed to the point of using more than 2-4 cores at the most.