And depending on his software, more GHz may offset more cores. I know this was true with my Ligthwave 3D package, where I had two servers rendering HD animations, one was setup with an i7-960 and the other had two Xeon processors for a total of 8 cores. I had the i7 OC'd to 4.6GHz and that offset the performance by the Xeon amount of cores by a 2 minute quicker rendering. i7s are great performance chips and much cheaper than Xeons, but nowadays there are soo many options with even relatively old chips, you can build yourself a monster multi-core xeon or Opteron server for little money.
Good write up btw.