Looking forward to seeing your results. We have a very similar set up, even including the rads. You posted several times in my about water blocks on the i7. Even though gabe said that I can't use the gtz 775 back plate on the P55 FTW, I still did. Well to be honest, I put the rig together before he replied and I wasn't going to use the stock cooler.

I think that the temps could be better and this can be attributed to the gtz's fitment. The back plate doesn't sit completely flush due to the socket's backplate screws. I still tightened it down and hoped for the best. Last time that I stressed the chip, it was running 4.2ghz with 1.37v under load with vdroop control enabled. It seems that when enabled, vcore shoots up when under load. With it disabled, vcore drops as is to be expected. Well, my temps were around 67°c with 80°F ambient.

Also, you said that your batch should be a decent clocker. Have you found a compiled list of batch numbers for the i5?