If you don't need raid or firewire go with the GA-p35-ds3l board and save $50 towards a better PSU
If you need FireWire: GA-P35-DS3P
If you need RAID or lots of SATA ports but not FireWire: GA-P35-DS3R
If you don't need RAID or FireWire and 4 SATA devices are plenty: GA-P35-DS3L
In any case, GA-P35C-DS3R makes you pay for DDR3 support and that's a waste.