Happy to help.... I figured that I should share back given how much great knowledge I have learned from you, and gained from this forum.
I continue to be amazed at how well an optimized xw6600 stands up to the Z600 and even the Z620 original motherboard workstations. I essentially follow the methods detailed above, and use two of the fastest quad core Xeons HP certified for the xw6600 (E5450, and specifically the SLBBM sSpec code version), and throw in one of those Intel 320 series SSDs, the USB3 card, and eSATA for fast external backup, and it just is a great combination.
For a student on a tight budget that is still the way to go, in my mind.
I have added the link below for others to see how I add in the eSATA and HP "2x2" 4 port USB3 card here.
Here is the Z600 with the USB3 card above the video card and the eSATA adapter in place, and the link above has some added good pictures:
