I don't think that there is any mac user that would agree that a p4 would be best in a G5 case. However, if you needed a pc, what case would you want? An ugly pc case? Not me, I would rather have a G5 case, presonally. However, I would never put a p4 in the case. I would absolutely stick with AMD. Just my thoughts.
"Fix it 'til it Breaks."

Jacob - EiC & Director of Technology
Mac Pro Quad 2.66 - 4GB RAM
160 GB SATA RAID 1 - 650 GB Storage
Quad 19" Widescreen LCDs
Accessorized to the Hilt