I would look for one of the p8p67 models from ASUS then get a full chipset water-cooling solution. The p8z68 works with the cooling blocks as well if you want SSD caching for some reason. The cash you save on the CPU and Motherboard you can put towards a really fine water loop and OC.http://www.frozencpu.com/products/12907/ex-blc-904/Heatkiller_MB-SET_ASUS_P8P67_Z68_LT_-_Full_Coverage_Water_Block_Kit_-_Acetal_Top_11401.html?tl=g30c89http://www.newegg.com/Product/Product.aspx?Item=N82E16813131771
I would go for this p67, but by the time the HD7990 you are wanting comes out the p8z68 may be cheaper. And remember PCIE 3.0 is just a sales gimick right now as no cards are able to saturate the 2.0 yet.
If you want gaming performance go for the 2500k (most people have to turn off hyperthreading to get the best OC/ Frames /second anyway).