I do all CAD everyday with mine. I draw House Plans. I don't really mess with Video but I often mess with large bitmaps of 100MB or more. 6GB works fine for me. I never said all the channels being full would cause a bottleneck. I said it would degrade your overclocking possibilities, you did say 4.5GHz. The 975 isn't going to guarantee you a stable overclock nor is the Classified Mobo. My i7 920 with a standard EVGA X58 mobo overclocks as well or better than alot of Classified mobo's and 975 cpu's.
But you said money was no object so go for the i7 975. And if money is no object and you want 12GB of memory then this is the kit for you
Newegg.com - Kingston HyperX 12GB (3 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model KHX12800D3K3/12GX - Desktop Memory
But you said money was no object so go for the i7 975. And if money is no object and you want 12GB of memory then this is the kit for you
Newegg.com - Kingston HyperX 12GB (3 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model KHX12800D3K3/12GX - Desktop Memory