Please get real. How many hand built machines have you built? Except for motherboards and cases, the same components are available to everyone. the same memory chips, the same video cards, the same SCSI cards, the same disk drives, the same DVD burners.
You want tank cases? Try Supermicro or LianLi, or even the server cases made for Dell or IBM.
As for motherboards and CPUs, I have seen exactly one Pentium, a 200, fail. I have never seen a motherboard fail except after a power surge. Nice thing about PC motherboards is you can hike down the street, pick up a replacement for $100 and be back in business the same day.
I wonder what iMac users will do for a backup monitor while their LCD is in the shop?
iMacs by default are dual monitor systems. You can take a standard VGA monitor and plug it into an iMac. So screw off the LCD and plug in the VGA monitor in the closet and go back to work.