Thanks SDH,
Many thanks for the information, (and after having a little break), I agree with your sentiments of separating the corporate HP from the employees . Essentially the Z620 was never designed to be a modders heaven but having such a powerful, stable work horse as a starting point is too much of a temptation, the HP build quality is the best I have used in terms of dual CPU systems.
Anyway, here's the worksheet I'm working from;
Essentially, I want to take advantage of my 1866MHz memory, (which is currently only running at 1600MHz due to my CPU's being E5-2670's v1). I looked at the quickspecs and created the above list of certified CPU's then proceeded to whittle down the list. My current PassMark dual CPU score is listed on the bottom row.
Started by ignoring all the E5-1600 series CPU's, followed by those that would not increase my ram speed, then passmark score, and finally ranking the remaining choices. I've already been searching ebay and realize that the minimum price will easily be in the £300-400+ mark for a single genuine production v2 CPU. I will be steering well clear of any cheaper ES or QS samples. I generally find that if you are patient enough, I wouldn't be surprised if I managed to buy a E5-2600 v2 CPU for nearer the £150-250 mark. (I manged to get my 2x E5-2670 for £115, K4200 for £275 and Tesla M2090 for £65 on ebay).
FYI,
I'm currently in the process of adding a Tesla M2090 to my Z620. I managed to get my quadro K4200 and Tesla M2090 running, (and benchmarked), simultaneously for a few minutes before the Tesla thermal shutdown kicked in. I am currently fitting a liquid cooling set-up and will post the full details when done. Using Octanebench, the K4200/Tesla M2090 maximus set-up, the score is the same as a quadro K6000 and marginally better than a quadro M5000.