Weighing in on the dual burners and HDDs, I can tell you that the Machine I finished building about 8 months ago (this machine, in fact) has twin DVD burners and twin HDDs.
I have had a minor issue with the twin burners that is probably easily remedied by someone more savvy than I. These burners are identical twins so, when burning to disk it is not uncommon to get confused as to which deck the app is referring to. Brassero and everything else I have used only refer to the decks by model number, (instead of unit #1 and #2) and the model numbers are obviously the same. It gets a bit old, switching disks back and forth to figure which burner the app is referring to and it is not consistantly the same one (because that would be too easy). My most recent solution is to load both burners with blanks and let the freaking machine pick the burner it wants to use that day.
Beware the jumpers that are factory-installed on Barracuda SATA drives !! Do not trust or believe the stickers that are attached to the hard drives and state that (1) no jumpers are needed, and (2) they are only installed for factory testing. Both of my Barracudas had jumpers installed, contrary to the stickers. Because these jumpers slow the drives down and will not allow them to be ATAPI compatible and recognized, it will make you plum crazy. The only thing that salvaged my sanity was my doubt that even I could get two doa hard drives, and I therefore found the installed jumpers.
One last tidbit of advice. Do NOT order only enough sata cables to get by, or fail to have the proper HDD and disc drive screws on hand. If your OEM drives come with screws, it is much more a fluke than the norm. You will not be a happy geek if you have to stop at that point and hunt down those itty-bitty screws. As to the cables, yeah, I know it's a ripoff what they charge to ship the darn things. But trust me on this- swapping out that defective cable with one you had the foresight to already buy beats the fire out of standing out at the curb waiting for that big brown truck to arrive. (Do I need to tell you how I know this?)
raphoenix has you covered on the rest of the stuff you need, so have fun and good luck. Oh, yeah, and pray.