I usually download the newest chipset, sata/raid, and device drivers from their respected web sites as the ones that come with your motherboard and other devices are usually out dated already.
After assembling the computer I then flash the bios to the newest version, and test ram using memtest86+. If memtest passes, then I install the os and drivers. I then stress test using prime95 running on all cores. If it passes prime95, then I image the drive before installing any programs. If you plan on OC'ing, now is the time to do it (before you install programs), being sure to stress test ram and cpu after each OC cycle.
Anyhow, that's just me. I'm sure others have their own roadmap they follow.
Since you are doing raid, you'll need to configure the raid bios and also the ahci/raid settings in your system bios before installing the OS.
Edit: Be sure to only have the OS drive/array installed before installing the OS. Add the other drives in later or you may end up with a boot loader on one drive and the OS on another.