What is “Best”? It is not difficult to come up with better HDD configurations, but it is always a matter of balancing cost and benefit. Your suggestion makes perfect sense if the storage capacity is sufficient.
If you want best, consider a 128 GB OCZ Core SSD as a boot disk for OS & programs.
For media, consider 8 x 1 TB WD Caviar Black disks in Raid50.
For project/scratch consider 4 x 1 TB WD Caviar Black disks in Raid3.
Make sure that all 12 disks are hot swappable and use an Areca ARC 1680iX-12 controller with BBM and 4 GB DDR2 ECC cache.
Harm Millaard