I wouldnt go with SLi if you plan on overclocking because the 680I's are behind with P35 and X38 being much better chipsets.
If you wish to go crossfire I suggest the DFI lanparty X38 or P35 motherboard
Ram go with crucial ballistix
if you want crossfire go with 750Quad with crossfire support unless the 610 does corssfire.
CAse Cosmos 1000, cooler amster 690 centurion 5 antec 900 etc.
750GB Seagate barracuda hdd.
LG or Samsung DVD burner