Looks like a fun build! ANd if you havent already bought the heatsinks, my supermicro 70mm tower coolers for socket 1207 will be available very shortly. Im interested to see how the modding of the lian-li goes as well, good luck with it!
Although i partially agree with whited that the G34 would be your best bet (plus you wouldn't have to mod the lian-li) but on the other hand the boards are almost impossible to find and the processors seem rare as well. On top of that, the best dodeca-core Opteron 6000-series tops out at 2.3Ghz right now. Whereas Istanbul, Shanghai and Barcelona Opterons can hit as high as 3.0ghz and are readily available, even through ebay. Just some food for thought